This function performs the following steps when called:

1. If value is present, then
   1. Let prim be ? ToNumeric(value).
   2. If prim is a BigInt, let n be 𝔽(ℝ(prim)).
   3. Otherwise, let n be prim.
2. Else,
   1. Let n be +0_𝔽.
3. If NewTarget is undefined, return n.
4. Let O be ? OrdinaryCreateFromConstructor(NewTarget, "%Number.prototype%", « [[NumberData]] »).
5. Set O.[[NumberData]] to n.
6. Return O.

The value of Number.EPSILON is the Number value for the magnitude of the difference between 1 and the smallest value greater than 1 that is representable as a Number value, which is approximately 2.2204460492503130808472633361816 × 10^-16.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

This function performs the following steps when called:

1. If number is not a Number, return false.
2. If number is not finite, return false.
3. Otherwise, return true.

This function performs the following steps when called:

1. Return IsIntegralNumber(number).

This function performs the following steps when called:

1. If number is not a Number, return false.
2. If number is NaN, return true.
3. Otherwise, return false.

Note

This function differs from the global isNaN function (19.2.3) in that it does not convert its argument to a Number before determining whether it is NaN.

Note

An integer n is considered "safe" if and only if the Number value for n is not the Number value for any other integer.

This function performs the following steps when called:

1. If IsIntegralNumber(number) is true, then
   1. If abs(ℝ(number)) ≤ 2⁵³ - 1, return true.
2. Return false.

Note

Due to rounding behaviour necessitated by precision limitations of IEEE 754-2019, the Number value for every integer greater than Number.MAX_SAFE_INTEGER is shared with at least one other integer. Such large-magnitude integers are therefore not safe, and are not guaranteed to be exactly representable as Number values or even to be distinguishable from each other. For example, both 9007199254740992 and 9007199254740993 evaluate to the Number value 9007199254740992_𝔽.

The value of Number.MAX_SAFE_INTEGER is 9007199254740991_𝔽 (𝔽(2⁵³ - 1)).

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The value of Number.MAX_VALUE is the largest positive finite value of the Number type, which is approximately 1.7976931348623157 × 10³⁰⁸.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

Note

Due to rounding behaviour necessitated by precision limitations of IEEE 754-2019, the Number value for every integer less than Number.MIN_SAFE_INTEGER is shared with at least one other integer. Such large-magnitude integers are therefore not safe, and are not guaranteed to be exactly representable as Number values or even to be distinguishable from each other. For example, both -9007199254740992 and -9007199254740993 evaluate to the Number value -9007199254740992_𝔽.

The value of Number.MIN_SAFE_INTEGER is -9007199254740991_𝔽 (𝔽(-(2⁵³ - 1))).

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The value of Number.MIN_VALUE is the smallest positive value of the Number type, which is approximately 5 × 10^-324.

In the IEEE 754-2019 double precision binary representation, the smallest possible value is a denormalized number. If an implementation does not support denormalized values, the value of Number.MIN_VALUE must be the smallest non-zero positive value that can actually be represented by the implementation.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The value of Number.NaN is NaN.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The value of Number.NEGATIVE_INFINITY is -∞_𝔽.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The initial value of the "parseFloat" property is %parseFloat%.

The initial value of the "parseInt" property is %parseInt%.

The value of Number.POSITIVE_INFINITY is +∞_𝔽.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The initial value of Number.prototype is the Number prototype object.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The initial value of Number.prototype.constructor is %Number%.

This method returns a String containing this Number value represented in decimal exponential notation with one digit before the significand's decimal point and fractionDigits digits after the significand's decimal point. If fractionDigits is undefined, it includes as many significand digits as necessary to uniquely specify the Number (just like in ToString except that in this case the Number is always output in exponential notation).

It performs the following steps when called:

1. Let x be ? thisNumberValue(this value).
2. Let f be ? ToIntegerOrInfinity(fractionDigits).
3. Assert: If fractionDigits is undefined, then f is 0.
4. If x is not finite, return Number::toString(x, 10).
5. If f < 0 or f > 100, throw a RangeError exception.
6. Set x to ℝ(x).
7. Let s be the empty String.
8. If x < 0, then
   1. Set s to "-".
   2. Set x to -x.
9. If x = 0, then
   1. Let m be the String value consisting of f + 1 occurrences of the code unit 0x0030 (DIGIT ZERO).
   2. Let e be 0.
10. Else,
    1. If fractionDigits is not undefined, then
       1. Let e and n be integers such that 10^f ≤ n < 10^{f + 1} and for which n × 10^{e - f} - x is as close to zero as possible. If there are two such sets of e and n, pick the e and n for which n × 10^{e - f} is larger.
    2. Else,
       1. Let e, n, and f be integers such that f ≥ 0, 10^f ≤ n < 10^{f + 1}, 𝔽(n × 10^{e - f}) is 𝔽(x), and f is as small as possible. Note that the decimal representation of n has f + 1 digits, n is not divisible by 10, and the least significant digit of n is not necessarily uniquely determined by these criteria.
    3. Let m be the String value consisting of the digits of the decimal representation of n (in order, with no leading zeroes).
11. If f ≠ 0, then
    1. Let a be the first code unit of m.
    2. Let b be the other f code units of m.
    3. Set m to the string-concatenation of a, ".", and b.
12. If e = 0, then
    1. Let c be "+".
    2. Let d be "0".
13. Else,
    1. If e > 0, let c be "+".
    2. Else,
       1. Assert: e < 0.
       2. Let c be "-".
       3. Set e to -e.
    3. Let d be the String value consisting of the digits of the decimal representation of e (in order, with no leading zeroes).
14. Set m to the string-concatenation of m, "e", c, and d.
15. Return the string-concatenation of s and m.

Note

For implementations that provide more accurate conversions than required by the rules above, it is recommended that the following alternative version of step 10.b.i be used as a guideline:

1. Let e, n, and f be integers such that f ≥ 0, 10^f ≤ n < 10^{f + 1}, 𝔽(n × 10^{e - f}) is 𝔽(x), and f is as small as possible. If there are multiple possibilities for n, choose the value of n for which 𝔽(n × 10^{e - f}) is closest in value to 𝔽(x). If there are two such possible values of n, choose the one that is even.

Note 1

This method returns a String containing this Number value represented in decimal fixed-point notation with fractionDigits digits after the decimal point. If fractionDigits is undefined, 0 is assumed.

It performs the following steps when called:

1. Let x be ? thisNumberValue(this value).
2. Let f be ? ToIntegerOrInfinity(fractionDigits).
3. Assert: If fractionDigits is undefined, then f is 0.
4. If f is not finite, throw a RangeError exception.
5. If f < 0 or f > 100, throw a RangeError exception.
6. If x is not finite, return Number::toString(x, 10).
7. Set x to ℝ(x).
8. Let s be the empty String.
9. If x < 0, then
   1. Set s to "-".
   2. Set x to -x.
10. If x ≥ 10²¹, then
    1. Let m be ! ToString(𝔽(x)).
11. Else,
    1. Let n be an integer for which n / 10^f - x is as close to zero as possible. If there are two such n, pick the larger n.
    2. If n = 0, let m be "0". Otherwise, let m be the String value consisting of the digits of the decimal representation of n (in order, with no leading zeroes).
    3. If f ≠ 0, then
       1. Let k be the length of m.
       2. If k ≤ f, then
          1. Let z be the String value consisting of f + 1 - k occurrences of the code unit 0x0030 (DIGIT ZERO).
          2. Set m to the string-concatenation of z and m.
          3. Set k to f + 1.
       3. Let a be the first k - f code units of m.
       4. Let b be the other f code units of m.
       5. Set m to the string-concatenation of a, ".", and b.
12. Return the string-concatenation of s and m.

Note 2

The output of toFixed may be more precise than toString for some values because toString only prints enough significant digits to distinguish the number from adjacent Number values. For example,

(1000000000000000128).toString() returns "1000000000000000100", while
(1000000000000000128).toFixed(0) returns "1000000000000000128".

An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement this method as specified in the ECMA-402 specification. If an ECMAScript implementation does not include the ECMA-402 API the following specification of this method is used:

This method produces a String value that represents this Number value formatted according to the conventions of the host environment's current locale. This method is implementation-defined, and it is permissible, but not encouraged, for it to return the same thing as toString.

The meanings of the optional parameters to this method are defined in the ECMA-402 specification; implementations that do not include ECMA-402 support must not use those parameter positions for anything else.

This method returns a String containing this Number value represented either in decimal exponential notation with one digit before the significand's decimal point and precision - 1 digits after the significand's decimal point or in decimal fixed notation with precision significant digits. If precision is undefined, it calls ToString instead.

It performs the following steps when called:

1. Let x be ? thisNumberValue(this value).
2. If precision is undefined, return ! ToString(x).
3. Let p be ? ToIntegerOrInfinity(precision).
4. If x is not finite, return Number::toString(x, 10).
5. If p < 1 or p > 100, throw a RangeError exception.
6. Set x to ℝ(x).
7. Let s be the empty String.
8. If x < 0, then
   1. Set s to the code unit 0x002D (HYPHEN-MINUS).
   2. Set x to -x.
9. If x = 0, then
   1. Let m be the String value consisting of p occurrences of the code unit 0x0030 (DIGIT ZERO).
   2. Let e be 0.
10. Else,
    1. Let e and n be integers such that 10^{p - 1} ≤ n < 10^p and for which n × 10^{e - p + 1} - x is as close to zero as possible. If there are two such sets of e and n, pick the e and n for which n × 10^{e - p + 1} is larger.
    2. Let m be the String value consisting of the digits of the decimal representation of n (in order, with no leading zeroes).
    3. If e < -6 or e ≥ p, then
       1. Assert: e ≠ 0.
       2. If p ≠ 1, then
          1. Let a be the first code unit of m.
          2. Let b be the other p - 1 code units of m.
          3. Set m to the string-concatenation of a, ".", and b.
       3. If e > 0, then
          1. Let c be the code unit 0x002B (PLUS SIGN).
       4. Else,
          1. Assert: e < 0.
          2. Let c be the code unit 0x002D (HYPHEN-MINUS).
          3. Set e to -e.
       5. Let d be the String value consisting of the digits of the decimal representation of e (in order, with no leading zeroes).
       6. Return the string-concatenation of s, m, the code unit 0x0065 (LATIN SMALL LETTER E), c, and d.
11. If e = p - 1, return the string-concatenation of s and m.
12. If e ≥ 0, then
    1. Set m to the string-concatenation of the first e + 1 code units of m, the code unit 0x002E (FULL STOP), and the remaining p - (e + 1) code units of m.
13. Else,
    1. Set m to the string-concatenation of the code unit 0x0030 (DIGIT ZERO), the code unit 0x002E (FULL STOP), -(e + 1) occurrences of the code unit 0x0030 (DIGIT ZERO), and the String m.
14. Return the string-concatenation of s and m.

Note

The optional radix should be an integral Number value in the inclusive interval from 2_𝔽 to 36_𝔽. If radix is undefined then 10_𝔽 is used as the value of radix.

This method performs the following steps when called:

1. Let x be ? thisNumberValue(this value).
2. If radix is undefined, let radixMV be 10.
3. Else, let radixMV be ? ToIntegerOrInfinity(radix).
4. If radixMV is not in the inclusive interval from 2 to 36, throw a RangeError exception.
5. Return Number::toString(x, radixMV).

This method is not generic; it throws a TypeError exception if its this value is not a Number or a Number object. Therefore, it cannot be transferred to other kinds of objects for use as a method.

The "length" property of this method is 1_𝔽.

1. Return ? thisNumberValue(this value).

This function performs the following steps when called:

1. If NewTarget is not undefined, throw a TypeError exception.
2. Let prim be ? ToPrimitive(value, number).
3. If prim is a Number, return ? NumberToBigInt(prim).
4. Otherwise, return ? ToBigInt(prim).

This function performs the following steps when called:

1. Set bits to ? ToIndex(bits).
2. Set bigint to ? ToBigInt(bigint).
3. Let mod be ℝ(bigint) modulo 2^bits.
4. If mod ≥ 2^{bits - 1}, return ℤ(mod - 2^bits); otherwise, return ℤ(mod).

This function performs the following steps when called:

1. Set bits to ? ToIndex(bits).
2. Set bigint to ? ToBigInt(bigint).
3. Return the BigInt value that represents ℝ(bigint) modulo 2^bits.

The initial value of BigInt.prototype is the BigInt prototype object.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The initial value of BigInt.prototype.constructor is %BigInt%.

An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement this method as specified in the ECMA-402 specification. If an ECMAScript implementation does not include the ECMA-402 API the following specification of this method is used:

This method produces a String value that represents this BigInt value formatted according to the conventions of the host environment's current locale. This method is implementation-defined, and it is permissible, but not encouraged, for it to return the same thing as toString.

The meanings of the optional parameters to this method are defined in the ECMA-402 specification; implementations that do not include ECMA-402 support must not use those parameter positions for anything else.

Note

The optional radix should be an integral Number value in the inclusive interval from 2_𝔽 to 36_𝔽. If radix is undefined then 10_𝔽 is used as the value of radix.

This method performs the following steps when called:

1. Let x be ? thisBigIntValue(this value).
2. If radix is undefined, let radixMV be 10.
3. Else, let radixMV be ? ToIntegerOrInfinity(radix).
4. If radixMV is not in the inclusive interval from 2 to 36, throw a RangeError exception.
5. Return BigInt::toString(x, radixMV).

This method is not generic; it throws a TypeError exception if its this value is not a BigInt or a BigInt object. Therefore, it cannot be transferred to other kinds of objects for use as a method.

1. Return ? thisBigIntValue(this value).

The initial value of the @@toStringTag property is the String value "BigInt".

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: true }.

The Number value for e, the base of the natural logarithms, which is approximately 2.7182818284590452354.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The Number value for the natural logarithm of 10, which is approximately 2.302585092994046.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The Number value for the natural logarithm of 2, which is approximately 0.6931471805599453.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The Number value for the base-10 logarithm of e, the base of the natural logarithms; this value is approximately 0.4342944819032518.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

Note

The value of Math.LOG10E is approximately the reciprocal of the value of Math.LN10.

The Number value for the base-2 logarithm of e, the base of the natural logarithms; this value is approximately 1.4426950408889634.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

Note

The value of Math.LOG2E is approximately the reciprocal of the value of Math.LN2.

The Number value for π, the ratio of the circumference of a circle to its diameter, which is approximately 3.1415926535897932.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The Number value for the square root of ½, which is approximately 0.7071067811865476.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

Note

The value of Math.SQRT1_2 is approximately the reciprocal of the value of Math.SQRT2.

The Number value for the square root of 2, which is approximately 1.4142135623730951.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

The initial value of the @@toStringTag property is the String value "Math".

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: true }.

This function returns the absolute value of x; the result has the same magnitude as x but has positive sign.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is NaN, return NaN.
3. If n is -0_𝔽, return +0_𝔽.
4. If n is -∞_𝔽, return +∞_𝔽.
5. If n < -0_𝔽, return -n.
6. Return n.

This function returns the inverse cosine of x. The result is expressed in radians and is in the inclusive interval from +0_𝔽 to 𝔽(π).

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is NaN, n > 1_𝔽, or n < -1_𝔽, return NaN.
3. If n is 1_𝔽, return +0_𝔽.
4. Return an implementation-approximated Number value representing the result of the inverse cosine of ℝ(n).

This function returns the inverse hyperbolic cosine of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is either NaN or +∞_𝔽, return n.
3. If n is 1_𝔽, return +0_𝔽.
4. If n < 1_𝔽, return NaN.
5. Return an implementation-approximated Number value representing the result of the inverse hyperbolic cosine of ℝ(n).

This function returns the inverse sine of x. The result is expressed in radians and is in the inclusive interval from 𝔽(-π / 2) to 𝔽(π / 2).

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is one of NaN, +0_𝔽, or -0_𝔽, return n.
3. If n > 1_𝔽 or n < -1_𝔽, return NaN.
4. Return an implementation-approximated Number value representing the result of the inverse sine of ℝ(n).

This function returns the inverse hyperbolic sine of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is not finite or n is either +0_𝔽 or -0_𝔽, return n.
3. Return an implementation-approximated Number value representing the result of the inverse hyperbolic sine of ℝ(n).

This function returns the inverse tangent of x. The result is expressed in radians and is in the inclusive interval from 𝔽(-π / 2) to 𝔽(π / 2).

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is one of NaN, +0_𝔽, or -0_𝔽, return n.
3. If n is +∞_𝔽, return an implementation-approximated Number value representing π / 2.
4. If n is -∞_𝔽, return an implementation-approximated Number value representing -π / 2.
5. Return an implementation-approximated Number value representing the result of the inverse tangent of ℝ(n).

This function returns the inverse hyperbolic tangent of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is one of NaN, +0_𝔽, or -0_𝔽, return n.
3. If n > 1_𝔽 or n < -1_𝔽, return NaN.
4. If n is 1_𝔽, return +∞_𝔽.
5. If n is -1_𝔽, return -∞_𝔽.
6. Return an implementation-approximated Number value representing the result of the inverse hyperbolic tangent of ℝ(n).

This function returns the inverse tangent of the quotient y / x of the arguments y and x, where the signs of y and x are used to determine the quadrant of the result. Note that it is intentional and traditional for the two-argument inverse tangent function that the argument named y be first and the argument named x be second. The result is expressed in radians and is in the inclusive interval from -π to +π.

It performs the following steps when called:

1. Let ny be ? ToNumber(y).
2. Let nx be ? ToNumber(x).
3. If ny is NaN or nx is NaN, return NaN.
4. If ny is +∞_𝔽, then
   1. If nx is +∞_𝔽, return an implementation-approximated Number value representing π / 4.
   2. If nx is -∞_𝔽, return an implementation-approximated Number value representing 3π / 4.
   3. Return an implementation-approximated Number value representing π / 2.
5. If ny is -∞_𝔽, then
   1. If nx is +∞_𝔽, return an implementation-approximated Number value representing -π / 4.
   2. If nx is -∞_𝔽, return an implementation-approximated Number value representing -3π / 4.
   3. Return an implementation-approximated Number value representing -π / 2.
6. If ny is +0_𝔽, then
   1. If nx > +0_𝔽 or nx is +0_𝔽, return +0_𝔽.
   2. Return an implementation-approximated Number value representing π.
7. If ny is -0_𝔽, then
   1. If nx > +0_𝔽 or nx is +0_𝔽, return -0_𝔽.
   2. Return an implementation-approximated Number value representing -π.
8. Assert: ny is finite and is neither +0_𝔽 nor -0_𝔽.
9. If ny > +0_𝔽, then
   1. If nx is +∞_𝔽, return +0_𝔽.
   2. If nx is -∞_𝔽, return an implementation-approximated Number value representing π.
   3. If nx is either +0_𝔽 or -0_𝔽, return an implementation-approximated Number value representing π / 2.
10. If ny < -0_𝔽, then
    1. If nx is +∞_𝔽, return -0_𝔽.
    2. If nx is -∞_𝔽, return an implementation-approximated Number value representing -π.
    3. If nx is either +0_𝔽 or -0_𝔽, return an implementation-approximated Number value representing -π / 2.
11. Assert: nx is finite and is neither +0_𝔽 nor -0_𝔽.
12. Return an implementation-approximated Number value representing the result of the inverse tangent of the quotient ℝ(ny) / ℝ(nx).

This function returns the cube root of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is not finite or n is either +0_𝔽 or -0_𝔽, return n.
3. Return an implementation-approximated Number value representing the result of the cube root of ℝ(n).

This function returns the smallest (closest to -∞) integral Number value that is not less than x. If x is already an integral Number, the result is x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is not finite or n is either +0_𝔽 or -0_𝔽, return n.
3. If n < -0_𝔽 and n > -1_𝔽, return -0_𝔽.
4. If n is an integral Number, return n.
5. Return the smallest (closest to -∞) integral Number value that is not less than n.

Note

The value of Math.ceil(x) is the same as the value of -Math.floor(-x).

This function performs the following steps when called:

1. Let n be ? ToUint32(x).
2. Let p be the number of leading zero bits in the unsigned 32-bit binary representation of n.
3. Return 𝔽(p).

Note

If n is either +0_𝔽 or -0_𝔽, this method returns 32_𝔽. If the most significant bit of the 32-bit binary encoding of n is 1, this method returns +0_𝔽.

This function returns the cosine of x. The argument is expressed in radians.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is not finite, return NaN.
3. If n is either +0_𝔽 or -0_𝔽, return 1_𝔽.
4. Return an implementation-approximated Number value representing the result of the cosine of ℝ(n).

This function returns the hyperbolic cosine of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is NaN, return NaN.
3. If n is either +∞_𝔽 or -∞_𝔽, return +∞_𝔽.
4. If n is either +0_𝔽 or -0_𝔽, return 1_𝔽.
5. Return an implementation-approximated Number value representing the result of the hyperbolic cosine of ℝ(n).

Note

The value of Math.cosh(x) is the same as the value of (Math.exp(x) + Math.exp(-x)) / 2.

This function returns the exponential function of x (e raised to the power of x, where e is the base of the natural logarithms).

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is either NaN or +∞_𝔽, return n.
3. If n is either +0_𝔽 or -0_𝔽, return 1_𝔽.
4. If n is -∞_𝔽, return +0_𝔽.
5. Return an implementation-approximated Number value representing the result of the exponential function of ℝ(n).

This function returns the result of subtracting 1 from the exponential function of x (e raised to the power of x, where e is the base of the natural logarithms). The result is computed in a way that is accurate even when the value of x is close to 0.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is one of NaN, +0_𝔽, -0_𝔽, or +∞_𝔽, return n.
3. If n is -∞_𝔽, return -1_𝔽.
4. Return an implementation-approximated Number value representing the result of subtracting 1 from the exponential function of ℝ(n).

This function returns the greatest (closest to +∞) integral Number value that is not greater than x. If x is already an integral Number, the result is x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is not finite or n is either +0_𝔽 or -0_𝔽, return n.
3. If n < 1_𝔽 and n > +0_𝔽, return +0_𝔽.
4. If n is an integral Number, return n.
5. Return the greatest (closest to +∞) integral Number value that is not greater than n.

Note

The value of Math.floor(x) is the same as the value of -Math.ceil(-x).

This function performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is NaN, return NaN.
3. If n is one of +0_𝔽, -0_𝔽, +∞_𝔽, or -∞_𝔽, return n.
4. Let n32 be the result of converting n to a value in IEEE 754-2019 binary32 format using roundTiesToEven mode.
5. Let n64 be the result of converting n32 to a value in IEEE 754-2019 binary64 format.
6. Return the ECMAScript Number value corresponding to n64.

Given zero or more arguments, this function returns the square root of the sum of squares of its arguments.

It performs the following steps when called:

1. Let coerced be a new empty List.
2. For each element arg of args, do
   1. Let n be ? ToNumber(arg).
   2. Append n to coerced.
3. For each element number of coerced, do
   1. If number is either +∞_𝔽 or -∞_𝔽, return +∞_𝔽.
4. Let onlyZero be true.
5. For each element number of coerced, do
   1. If number is NaN, return NaN.
   2. If number is neither +0_𝔽 nor -0_𝔽, set onlyZero to false.
6. If onlyZero is true, return +0_𝔽.
7. Return an implementation-approximated Number value representing the square root of the sum of squares of the mathematical values of the elements of coerced.

The "length" property of this function is 2_𝔽.

Note

Implementations should take care to avoid the loss of precision from overflows and underflows that are prone to occur in naive implementations when this function is called with two or more arguments.

This function performs the following steps when called:

1. Let a be ℝ(? ToUint32(x)).
2. Let b be ℝ(? ToUint32(y)).
3. Let product be (a × b) modulo 2³².
4. If product ≥ 2³¹, return 𝔽(product - 2³²); otherwise return 𝔽(product).

This function returns the natural logarithm of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is either NaN or +∞_𝔽, return n.
3. If n is 1_𝔽, return +0_𝔽.
4. If n is either +0_𝔽 or -0_𝔽, return -∞_𝔽.
5. If n < -0_𝔽, return NaN.
6. Return an implementation-approximated Number value representing the result of the natural logarithm of ℝ(n).

This function returns the natural logarithm of 1 + x. The result is computed in a way that is accurate even when the value of x is close to zero.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is one of NaN, +0_𝔽, -0_𝔽, or +∞_𝔽, return n.
3. If n is -1_𝔽, return -∞_𝔽.
4. If n < -1_𝔽, return NaN.
5. Return an implementation-approximated Number value representing the result of the natural logarithm of 1 + ℝ(n).

This function returns the base 10 logarithm of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is either NaN or +∞_𝔽, return n.
3. If n is 1_𝔽, return +0_𝔽.
4. If n is either +0_𝔽 or -0_𝔽, return -∞_𝔽.
5. If n < -0_𝔽, return NaN.
6. Return an implementation-approximated Number value representing the result of the base 10 logarithm of ℝ(n).

This function returns the base 2 logarithm of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is either NaN or +∞_𝔽, return n.
3. If n is 1_𝔽, return +0_𝔽.
4. If n is either +0_𝔽 or -0_𝔽, return -∞_𝔽.
5. If n < -0_𝔽, return NaN.
6. Return an implementation-approximated Number value representing the result of the base 2 logarithm of ℝ(n).

Given zero or more arguments, this function calls ToNumber on each of the arguments and returns the largest of the resulting values.

It performs the following steps when called:

1. Let coerced be a new empty List.
2. For each element arg of args, do
   1. Let n be ? ToNumber(arg).
   2. Append n to coerced.
3. Let highest be -∞_𝔽.
4. For each element number of coerced, do
   1. If number is NaN, return NaN.
   2. If number is +0_𝔽 and highest is -0_𝔽, set highest to +0_𝔽.
   3. If number > highest, set highest to number.
5. Return highest.

Note

The comparison of values to determine the largest value is done using the IsLessThan algorithm except that +0_𝔽 is considered to be larger than -0_𝔽.

The "length" property of this function is 2_𝔽.

Given zero or more arguments, this function calls ToNumber on each of the arguments and returns the smallest of the resulting values.

It performs the following steps when called:

1. Let coerced be a new empty List.
2. For each element arg of args, do
   1. Let n be ? ToNumber(arg).
   2. Append n to coerced.
3. Let lowest be +∞_𝔽.
4. For each element number of coerced, do
   1. If number is NaN, return NaN.
   2. If number is -0_𝔽 and lowest is +0_𝔽, set lowest to -0_𝔽.
   3. If number < lowest, set lowest to number.
5. Return lowest.

Note

The comparison of values to determine the largest value is done using the IsLessThan algorithm except that +0_𝔽 is considered to be larger than -0_𝔽.

The "length" property of this function is 2_𝔽.

This function performs the following steps when called:

1. Set base to ? ToNumber(base).
2. Set exponent to ? ToNumber(exponent).
3. Return Number::exponentiate(base, exponent).

This function returns a Number value with positive sign, greater than or equal to +0_𝔽 but strictly less than 1_𝔽, chosen randomly or pseudo randomly with approximately uniform distribution over that range, using an implementation-defined algorithm or strategy.

Each Math.random function created for distinct realms must produce a distinct sequence of values from successive calls.

This function returns the Number value that is closest to x and is integral. If two integral Numbers are equally close to x, then the result is the Number value that is closer to +∞. If x is already integral, the result is x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is not finite or n is an integral Number, return n.
3. If n < 0.5_𝔽 and n > +0_𝔽, return +0_𝔽.
4. If n < -0_𝔽 and n ≥ -0.5_𝔽, return -0_𝔽.
5. Return the integral Number closest to n, preferring the Number closer to +∞ in the case of a tie.

Note 1

Math.round(3.5) returns 4, but Math.round(-3.5) returns -3.

Note 2

The value of Math.round(x) is not always the same as the value of Math.floor(x + 0.5). When x is -0_𝔽 or x is less than +0_𝔽 but greater than or equal to -0.5_𝔽, Math.round(x) returns -0_𝔽, but Math.floor(x + 0.5) returns +0_𝔽. Math.round(x) may also differ from the value of Math.floor(x + 0.5)because of internal rounding when computing x + 0.5.

This function returns the sign of x, indicating whether x is positive, negative, or zero.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is one of NaN, +0_𝔽, or -0_𝔽, return n.
3. If n < -0_𝔽, return -1_𝔽.
4. Return 1_𝔽.

This function returns the sine of x. The argument is expressed in radians.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is one of NaN, +0_𝔽, or -0_𝔽, return n.
3. If n is either +∞_𝔽 or -∞_𝔽, return NaN.
4. Return an implementation-approximated Number value representing the result of the sine of ℝ(n).

This function returns the hyperbolic sine of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is not finite or n is either +0_𝔽 or -0_𝔽, return n.
3. Return an implementation-approximated Number value representing the result of the hyperbolic sine of ℝ(n).

Note

The value of Math.sinh(x) is the same as the value of (Math.exp(x) - Math.exp(-x)) / 2.

This function returns the square root of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is one of NaN, +0_𝔽, -0_𝔽, or +∞_𝔽, return n.
3. If n < -0_𝔽, return NaN.
4. Return an implementation-approximated Number value representing the result of the square root of ℝ(n).

This function returns the tangent of x. The argument is expressed in radians.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is one of NaN, +0_𝔽, or -0_𝔽, return n.
3. If n is either +∞_𝔽 or -∞_𝔽, return NaN.
4. Return an implementation-approximated Number value representing the result of the tangent of ℝ(n).

This function returns the hyperbolic tangent of x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is one of NaN, +0_𝔽, or -0_𝔽, return n.
3. If n is +∞_𝔽, return 1_𝔽.
4. If n is -∞_𝔽, return -1_𝔽.
5. Return an implementation-approximated Number value representing the result of the hyperbolic tangent of ℝ(n).

Note

The value of Math.tanh(x) is the same as the value of (Math.exp(x) - Math.exp(-x)) / (Math.exp(x) + Math.exp(-x)).

This function returns the integral part of the number x, removing any fractional digits. If x is already integral, the result is x.

It performs the following steps when called:

1. Let n be ? ToNumber(x).
2. If n is not finite or n is either +0_𝔽 or -0_𝔽, return n.
3. If n < 1_𝔽 and n > +0_𝔽, return +0_𝔽.
4. If n < -0_𝔽 and n > -1_𝔽, return -0_𝔽.
5. Return the integral Number nearest n in the direction of +0_𝔽.

Time measurement in ECMAScript is analogous to time measurement in POSIX, in particular sharing definition in terms of the proleptic Gregorian calendar, an epoch of midnight at the beginning of 1 January 1970 UTC, and an accounting of every day as comprising exactly 86,400 seconds (each of which is 1000 milliseconds long).

An ECMAScript time value is a Number, either a finite integral Number representing an instant in time to millisecond precision or NaN representing no specific instant. A time value that is a multiple of 24 × 60 × 60 × 1000 = 86,400,000 (i.e., is 86,400,000 × d for some integer d) represents the instant at the start of the UTC day that follows the epoch by d whole UTC days (preceding the epoch for negative d). Every other finite time value t is defined relative to the greatest preceding time value s that is such a multiple, and represents the instant that occurs within the same UTC day as s but follows it by (t - s) milliseconds.

Time values do not account for UTC leap seconds—there are no time values representing instants within positive leap seconds, and there are time values representing instants removed from the UTC timeline by negative leap seconds. However, the definition of time values nonetheless yields piecewise alignment with UTC, with discontinuities only at leap second boundaries and zero difference outside of leap seconds.

A Number can exactly represent all integers from -9,007,199,254,740,992 to 9,007,199,254,740,992 (21.1.2.8 and 21.1.2.6). A time value supports a slightly smaller range of -8,640,000,000,000,000 to 8,640,000,000,000,000 milliseconds. This yields a supported time value range of exactly -100,000,000 days to 100,000,000 days relative to midnight at the beginning of 1 January 1970 UTC.

The exact moment of midnight at the beginning of 1 January 1970 UTC is represented by the time value +0_𝔽.

Note

The 400 year cycle of the proleptic Gregorian calendar contains 97 leap years. This yields an average of 365.2425 days per year, which is 31,556,952,000 milliseconds. Therefore, the maximum range a Number could represent exactly with millisecond precision is approximately -285,426 to 285,426 years relative to 1970. The smaller range supported by a time value as specified in this section is approximately -273,790 to 273,790 years relative to 1970.

A given time value t belongs to day number

Day(t) = 𝔽(floor(ℝ(t / msPerDay)))

where the number of milliseconds per day is

msPerDay = 86400000_𝔽

The remainder is called the time within the day:

TimeWithinDay(t) = 𝔽(ℝ(t) modulo ℝ(msPerDay))

ECMAScript uses a proleptic Gregorian calendar to map a day number to a year number and to determine the month and date within that year. In this calendar, leap years are precisely those which are (divisible by 4) and ((not divisible by 100) or (divisible by 400)). The number of days in year number y is therefore defined by

DaysInYear(y) = 365_𝔽 if (ℝ(y) modulo 4) ≠ 0 = 366_𝔽 if (ℝ(y) modulo 4) = 0 and (ℝ(y) modulo 100) ≠ 0 = 365_𝔽 if (ℝ(y) modulo 100) = 0 and (ℝ(y) modulo 400) ≠ 0 = 366_𝔽 if (ℝ(y) modulo 400) = 0

All non-leap years have 365 days with the usual number of days per month and leap years have an extra day in February. The day number of the first day of year y is given by:

DayFromYear(y) = 𝔽(365 × (ℝ(y) - 1970) + floor((ℝ(y) - 1969) / 4) - floor((ℝ(y) - 1901) / 100) + floor((ℝ(y) - 1601) / 400))

The time value of the start of a year is:

TimeFromYear(y) = msPerDay × DayFromYear(y)

A time value determines a year by:

YearFromTime(t) = the largest integral Number y (closest to +∞) such that TimeFromYear(y) ≤ t

The leap-year function is 1_𝔽 for a time within a leap year and otherwise is +0_𝔽:

InLeapYear(t) = +0_𝔽 if DaysInYear(YearFromTime(t)) is 365_𝔽 = 1_𝔽 if DaysInYear(YearFromTime(t)) is 366_𝔽

Months are identified by an integral Number in the inclusive interval from +0_𝔽 to 11_𝔽. The mapping MonthFromTime(t) from a time value t to a month number is defined by:

MonthFromTime(t) = +0_𝔽 if +0_𝔽 ≤ DayWithinYear(t) < 31_𝔽 = 1_𝔽 if 31_𝔽 ≤ DayWithinYear(t) < 59_𝔽 + InLeapYear(t) = 2_𝔽 if 59_𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 90_𝔽 + InLeapYear(t) = 3_𝔽 if 90_𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 120_𝔽 + InLeapYear(t) = 4_𝔽 if 120_𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 151_𝔽 + InLeapYear(t) = 5_𝔽 if 151_𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 181_𝔽 + InLeapYear(t) = 6_𝔽 if 181_𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 212_𝔽 + InLeapYear(t) = 7_𝔽 if 212_𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 243_𝔽 + InLeapYear(t) = 8_𝔽 if 243_𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 273_𝔽 + InLeapYear(t) = 9_𝔽 if 273_𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 304_𝔽 + InLeapYear(t) = 10_𝔽 if 304_𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 334_𝔽 + InLeapYear(t) = 11_𝔽 if 334_𝔽 + InLeapYear(t) ≤ DayWithinYear(t) < 365_𝔽 + InLeapYear(t)

where

DayWithinYear(t) = Day(t) - DayFromYear(YearFromTime(t))

A month value of +0_𝔽 specifies January; 1_𝔽 specifies February; 2_𝔽 specifies March; 3_𝔽 specifies April; 4_𝔽 specifies May; 5_𝔽 specifies June; 6_𝔽 specifies July; 7_𝔽 specifies August; 8_𝔽 specifies September; 9_𝔽 specifies October; 10_𝔽 specifies November; and 11_𝔽 specifies December. Note that MonthFromTime(+0_𝔽) = +0_𝔽, corresponding to Thursday, 1 January 1970.

A date number is identified by an integral Number in the inclusive interval from 1_𝔽 to 31_𝔽. The mapping DateFromTime(t) from a time value t to a date number is defined by:

DateFromTime(t) = DayWithinYear(t) + 1_𝔽 if MonthFromTime(t) is +0_𝔽 = DayWithinYear(t) - 30_𝔽 if MonthFromTime(t) is 1_𝔽 = DayWithinYear(t) - 58_𝔽 - InLeapYear(t) if MonthFromTime(t) is 2_𝔽 = DayWithinYear(t) - 89_𝔽 - InLeapYear(t) if MonthFromTime(t) is 3_𝔽 = DayWithinYear(t) - 119_𝔽 - InLeapYear(t) if MonthFromTime(t) is 4_𝔽 = DayWithinYear(t) - 150_𝔽 - InLeapYear(t) if MonthFromTime(t) is 5_𝔽 = DayWithinYear(t) - 180_𝔽 - InLeapYear(t) if MonthFromTime(t) is 6_𝔽 = DayWithinYear(t) - 211_𝔽 - InLeapYear(t) if MonthFromTime(t) is 7_𝔽 = DayWithinYear(t) - 242_𝔽 - InLeapYear(t) if MonthFromTime(t) is 8_𝔽 = DayWithinYear(t) - 272_𝔽 - InLeapYear(t) if MonthFromTime(t) is 9_𝔽 = DayWithinYear(t) - 303_𝔽 - InLeapYear(t) if MonthFromTime(t) is 10_𝔽 = DayWithinYear(t) - 333_𝔽 - InLeapYear(t) if MonthFromTime(t) is 11_𝔽

The weekday for a particular time value t is defined as

WeekDay(t) = 𝔽(ℝ(Day(t) + 4_𝔽) modulo 7)

A weekday value of +0_𝔽 specifies Sunday; 1_𝔽 specifies Monday; 2_𝔽 specifies Tuesday; 3_𝔽 specifies Wednesday; 4_𝔽 specifies Thursday; 5_𝔽 specifies Friday; and 6_𝔽 specifies Saturday. Note that WeekDay(+0_𝔽) = 4_𝔽, corresponding to Thursday, 1 January 1970.

The abstract operation GetUTCEpochNanoseconds takes arguments year (an integer), month (an integer in the inclusive interval from 1 to 12), day (an integer in the inclusive interval from 1 to 31), hour (an integer in the inclusive interval from 0 to 23), minute (an integer in the inclusive interval from 0 to 59), second (an integer in the inclusive interval from 0 to 59), millisecond (an integer in the inclusive interval from 0 to 999), microsecond (an integer in the inclusive interval from 0 to 999), and nanosecond (an integer in the inclusive interval from 0 to 999) and returns a BigInt. The returned value represents a number of nanoseconds since the epoch that corresponds to the given ISO 8601 calendar date and wall-clock time in UTC. It performs the following steps when called:

1. Let date be MakeDay(𝔽(year), 𝔽(month - 1), 𝔽(day)).
2. Let time be MakeTime(𝔽(hour), 𝔽(minute), 𝔽(second), 𝔽(millisecond)).
3. Let ms be MakeDate(date, time).
4. Assert: ms is an integral Number.
5. Return ℤ(ℝ(ms) × 10⁶ + microsecond × 10³ + nanosecond).

The implementation-defined abstract operation GetNamedTimeZoneEpochNanoseconds takes arguments timeZoneIdentifier (a String), year (an integer), month (an integer in the inclusive interval from 1 to 12), day (an integer in the inclusive interval from 1 to 31), hour (an integer in the inclusive interval from 0 to 23), minute (an integer in the inclusive interval from 0 to 59), second (an integer in the inclusive interval from 0 to 59), millisecond (an integer in the inclusive interval from 0 to 999), microsecond (an integer in the inclusive interval from 0 to 999), and nanosecond (an integer in the inclusive interval from 0 to 999) and returns a List of BigInts. Each value in the returned List represents a number of nanoseconds since the epoch that corresponds to the given ISO 8601 calendar date and wall-clock time in the named time zone identified by timeZoneIdentifier.

When the input represents a local time occurring more than once because of a negative time zone transition (e.g. when daylight saving time ends or the time zone offset is decreased due to a time zone rule change), the returned List will have more than one element and will be sorted by ascending numerical value. When the input represents a local time skipped because of a positive time zone transition (e.g. when daylight saving time begins or the time zone offset is increased due to a time zone rule change), the returned List will be empty. Otherwise, the returned List will have one element.

The default implementation of GetNamedTimeZoneEpochNanoseconds, to be used for ECMAScript implementations that do not include local political rules for any time zones, performs the following steps when called:

1. Assert: timeZoneIdentifier is "UTC".
2. Let epochNanoseconds be GetUTCEpochNanoseconds(year, month, day, hour, minute, second, millisecond, microsecond, nanosecond).
3. Return « epochNanoseconds ».

Note

It is recommended that implementations use the time zone information of the IANA Time Zone Database https://www.iana.org/time-zones/.

1:30 AM on 5 November 2017 in America/New_York is repeated twice, so GetNamedTimeZoneEpochNanoseconds("America/New_York", 2017, 11, 5, 1, 30, 0, 0, 0, 0) would return a List of length 2 in which the first element represents 05:30 UTC (corresponding with 01:30 US Eastern Daylight Time at UTC offset -04:00) and the second element represents 06:30 UTC (corresponding with 01:30 US Eastern Standard Time at UTC offset -05:00).

2:30 AM on 12 March 2017 in America/New_York does not exist, so GetNamedTimeZoneEpochNanoseconds("America/New_York", 2017, 3, 12, 2, 30, 0, 0, 0, 0) would return an empty List.

The implementation-defined abstract operation GetNamedTimeZoneOffsetNanoseconds takes arguments timeZoneIdentifier (a String) and epochNanoseconds (a BigInt) and returns an integer.

The returned integer represents the offset from UTC of the named time zone identified by timeZoneIdentifier, at the instant corresponding with epochNanoseconds relative to the epoch, both in nanoseconds.

The default implementation of GetNamedTimeZoneOffsetNanoseconds, to be used for ECMAScript implementations that do not include local political rules for any time zones, performs the following steps when called:

1. Assert: timeZoneIdentifier is "UTC".
2. Return 0.

Note

Time zone offset values may be positive or negative.

The implementation-defined abstract operation DefaultTimeZone takes no arguments and returns a String. It returns a String value representing the host environment's current time zone, which is either a String representing a UTC offset for which IsTimeZoneOffsetString returns true, or a String identifier accepted by GetNamedTimeZoneEpochNanoseconds and GetNamedTimeZoneOffsetNanoseconds.

An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement the DefaultTimeZone abstract operation as specified in the ECMA-402 specification.

The default implementation of DefaultTimeZone, to be used for ECMAScript implementations that do not include local political rules for any time zones, performs the following steps when called:

1. Return "UTC".

Note

To ensure the level of functionality that implementations commonly provide in the methods of the Date object, it is recommended that DefaultTimeZone return an IANA time zone name corresponding to the host environment's time zone setting, if such a thing exists. GetNamedTimeZoneEpochNanoseconds and GetNamedTimeZoneOffsetNanoseconds must reflect the local political rules for standard time and daylight saving time in that time zone, if such rules exist.

For example, if the host environment is a browser on a system where the user has chosen US Eastern Time as their time zone, DefaultTimeZone returns "America/New_York".

The abstract operation LocalTime takes argument t (a finite time value) and returns an integral Number. It converts t from UTC to local time. The local political rules for standard time and daylight saving time in effect at t should be used to determine the result in the way specified in this section. It performs the following steps when called:

1. Let localTimeZone be DefaultTimeZone().
2. If IsTimeZoneOffsetString(localTimeZone) is true, then
   1. Let offsetNs be ParseTimeZoneOffsetString(localTimeZone).
3. Else,
   1. Let offsetNs be GetNamedTimeZoneOffsetNanoseconds(localTimeZone, ℤ(ℝ(t) × 10⁶)).
4. Let offsetMs be truncate(offsetNs / 10⁶).
5. Return t + 𝔽(offsetMs).

If political rules for the local time t are not available within the implementation, the result is t because DefaultTimeZone returns "UTC" and GetNamedTimeZoneOffsetNanoseconds returns 0.

Note 1

It is recommended that implementations use the time zone information of the IANA Time Zone Database https://www.iana.org/time-zones/.

Note 2

Two different input time values t_UTC are converted to the same local time t_local at a negative time zone transition when there are repeated times (e.g. the daylight saving time ends or the time zone adjustment is decreased.).

LocalTime(UTC(t_local)) is not necessarily always equal to t_local. Correspondingly, UTC(LocalTime(t_UTC)) is not necessarily always equal to t_UTC.

The abstract operation UTC takes argument t (a Number) and returns a time value. It converts t from local time to a UTC time value. The local political rules for standard time and daylight saving time in effect at t should be used to determine the result in the way specified in this section. It performs the following steps when called:

1. Let localTimeZone be DefaultTimeZone().
2. If IsTimeZoneOffsetString(localTimeZone) is true, then
   1. Let offsetNs be ParseTimeZoneOffsetString(localTimeZone).
3. Else,
   1. Let possibleInstants be GetNamedTimeZoneEpochNanoseconds(localTimeZone, ℝ(YearFromTime(t)), ℝ(MonthFromTime(t)) + 1, ℝ(DateFromTime(t)), ℝ(HourFromTime(t)), ℝ(MinFromTime(t)), ℝ(SecFromTime(t)), ℝ(msFromTime(t)), 0, 0).
   2. NOTE: The following steps ensure that when t represents local time repeating multiple times at a negative time zone transition (e.g. when the daylight saving time ends or the time zone offset is decreased due to a time zone rule change) or skipped local time at a positive time zone transition (e.g. when the daylight saving time starts or the time zone offset is increased due to a time zone rule change), t is interpreted using the time zone offset before the transition.
   3. If possibleInstants is not empty, then
      1. Let disambiguatedInstant be possibleInstants[0].
   4. Else,
      1. NOTE: t represents a local time skipped at a positive time zone transition (e.g. due to daylight saving time starting or a time zone rule change increasing the UTC offset).
      2. Let possibleInstantsBefore be GetNamedTimeZoneEpochNanoseconds(localTimeZone, ℝ(YearFromTime(tBefore)), ℝ(MonthFromTime(tBefore)) + 1, ℝ(DateFromTime(tBefore)), ℝ(HourFromTime(tBefore)), ℝ(MinFromTime(tBefore)), ℝ(SecFromTime(tBefore)), ℝ(msFromTime(tBefore)), 0, 0), where tBefore is the largest integral Number < t for which possibleInstantsBefore is not empty (i.e., tBefore represents the last local time before the transition).
      3. Let disambiguatedInstant be the last element of possibleInstantsBefore.
   5. Let offsetNs be GetNamedTimeZoneOffsetNanoseconds(localTimeZone, disambiguatedInstant).
4. Let offsetMs be truncate(offsetNs / 10⁶).
5. Return t - 𝔽(offsetMs).

Input t is nominally a time value but may be any Number value. The algorithm must not limit t to the time value range, so that inputs corresponding with a boundary of the time value range can be supported regardless of local UTC offset. For example, the maximum time value is 8.64 × 10¹⁵, corresponding with "+275760-09-13T00:00:00Z". In an environment where the local time zone offset is ahead of UTC by 1 hour at that instant, it is represented by the larger input of 8.64 × 10¹⁵ + 3.6 × 10⁶, corresponding with "+275760-09-13T01:00:00+01:00".

If political rules for the local time t are not available within the implementation, the result is t because DefaultTimeZone returns "UTC" and GetNamedTimeZoneOffsetNanoseconds returns 0.

Note 1

It is recommended that implementations use the time zone information of the IANA Time Zone Database https://www.iana.org/time-zones/.

1:30 AM on 5 November 2017 in America/New_York is repeated twice (fall backward), but it must be interpreted as 1:30 AM UTC-04 instead of 1:30 AM UTC-05. In UTC(TimeClip(MakeDate(MakeDay(2017, 10, 5), MakeTime(1, 30, 0, 0)))), the value of offsetMs is -4 × msPerHour.

2:30 AM on 12 March 2017 in America/New_York does not exist, but it must be interpreted as 2:30 AM UTC-05 (equivalent to 3:30 AM UTC-04). In UTC(TimeClip(MakeDate(MakeDay(2017, 2, 12), MakeTime(2, 30, 0, 0)))), the value of offsetMs is -5 × msPerHour.

Note 2

UTC(LocalTime(t_UTC)) is not necessarily always equal to t_UTC. Correspondingly, LocalTime(UTC(t_local)) is not necessarily always equal to t_local.

The following abstract operations are useful in decomposing time values:

HourFromTime(t) = 𝔽(floor(ℝ(t / msPerHour)) modulo HoursPerDay) MinFromTime(t) = 𝔽(floor(ℝ(t / msPerMinute)) modulo MinutesPerHour) SecFromTime(t) = 𝔽(floor(ℝ(t / msPerSecond)) modulo SecondsPerMinute) msFromTime(t) = 𝔽(ℝ(t) modulo ℝ(msPerSecond))

where

HoursPerDay = 24 MinutesPerHour = 60 SecondsPerMinute = 60 msPerSecond = 1000_𝔽 msPerMinute = 60000_𝔽 = msPerSecond × 𝔽(SecondsPerMinute) msPerHour = 3600000_𝔽 = msPerMinute × 𝔽(MinutesPerHour)

The abstract operation MakeTime takes arguments hour (a Number), min (a Number), sec (a Number), and ms (a Number) and returns a Number. It calculates a number of milliseconds. It performs the following steps when called:

1. If hour is not finite, min is not finite, sec is not finite, or ms is not finite, return NaN.
2. Let h be 𝔽(! ToIntegerOrInfinity(hour)).
3. Let m be 𝔽(! ToIntegerOrInfinity(min)).
4. Let s be 𝔽(! ToIntegerOrInfinity(sec)).
5. Let milli be 𝔽(! ToIntegerOrInfinity(ms)).
6. Let t be ((h * msPerHour + m * msPerMinute) + s * msPerSecond) + milli, performing the arithmetic according to IEEE 754-2019 rules (that is, as if using the ECMAScript operators * and +).
7. Return t.

The abstract operation MakeDay takes arguments year (a Number), month (a Number), and date (a Number) and returns a Number. It calculates a number of days. It performs the following steps when called:

1. If year is not finite, month is not finite, or date is not finite, return NaN.
2. Let y be 𝔽(! ToIntegerOrInfinity(year)).
3. Let m be 𝔽(! ToIntegerOrInfinity(month)).
4. Let dt be 𝔽(! ToIntegerOrInfinity(date)).
5. Let ym be y + 𝔽(floor(ℝ(m) / 12)).
6. If ym is not finite, return NaN.
7. Let mn be 𝔽(ℝ(m) modulo 12).
8. Find a finite time value t such that YearFromTime(t) is ym, MonthFromTime(t) is mn, and DateFromTime(t) is 1_𝔽; but if this is not possible (because some argument is out of range), return NaN.
9. Return Day(t) + dt - 1_𝔽.

The abstract operation MakeDate takes arguments day (a Number) and time (a Number) and returns a Number. It calculates a number of milliseconds. It performs the following steps when called:

1. If day is not finite or time is not finite, return NaN.
2. Let tv be day × msPerDay + time.
3. If tv is not finite, return NaN.
4. Return tv.

The abstract operation TimeClip takes argument time (a Number) and returns a Number. It calculates a number of milliseconds. It performs the following steps when called:

1. If time is not finite, return NaN.
2. If abs(ℝ(time)) > 8.64 × 10¹⁵, return NaN.
3. Return 𝔽(! ToIntegerOrInfinity(time)).

ECMAScript defines a string interchange format for date-times based upon a simplification of the ISO 8601 calendar date extended format. The format is as follows: YYYY-MM-DDTHH:mm:ss.sssZ

Where the elements are as follows:

YYYY	is the year in the proleptic Gregorian calendar as four decimal digits from 0000 to 9999, or as an expanded year of "+" or "-" followed by six decimal digits.
-	"-" (hyphen) appears literally twice in the string.
MM	is the month of the year as two decimal digits from 01 (January) to 12 (December).
DD	is the day of the month as two decimal digits from 01 to 31.
T	"T" appears literally in the string, to indicate the beginning of the time element.
HH	is the number of complete hours that have passed since midnight as two decimal digits from 00 to 24.
:	":" (colon) appears literally twice in the string.
mm	is the number of complete minutes since the start of the hour as two decimal digits from 00 to 59.
ss	is the number of complete seconds since the start of the minute as two decimal digits from 00 to 59.
.	"." (dot) appears literally in the string.
sss	is the number of complete milliseconds since the start of the second as three decimal digits.
Z	is the UTC offset representation specified as "Z" (for UTC with no offset) or as either "+" or "-" followed by a time expression HH:mm (a subset of the time zone offset string format for indicating local time ahead of or behind UTC, respectively)

This format includes date-only forms:

YYYY
YYYY-MM
YYYY-MM-DD
        

It also includes “date-time” forms that consist of one of the above date-only forms immediately followed by one of the following time forms with an optional UTC offset representation appended:

THH:mm
THH:mm:ss
THH:mm:ss.sss
        

A string containing out-of-bounds or nonconforming elements is not a valid instance of this format.

Note 1

As every day both starts and ends with midnight, the two notations 00:00 and 24:00 are available to distinguish the two midnights that can be associated with one date. This means that the following two notations refer to exactly the same point in time: 1995-02-04T24:00 and 1995-02-05T00:00. This interpretation of the latter form as "end of a calendar day" is consistent with ISO 8601, even though that specification reserves it for describing time intervals and does not permit it within representations of single points in time.

Note 2

There exists no international standard that specifies abbreviations for civil time zones like CET, EST, etc. and sometimes the same abbreviation is even used for two very different time zones. For this reason, both ISO 8601 and this format specify numeric representations of time zone offsets.

ECMAScript defines a string interchange format for UTC offsets, derived from ISO 8601. The format is described by the following grammar. The usage of Unicode code points in this grammar is listed in Table 60.

Code Point	Unicode Name	Abbreviation
U+2212	MINUS SIGN	<MINUS>

Syntax

UTCOffset ::: TemporalSign Hour TemporalSign Hour HourSubcomponents[+Extended] TemporalSign Hour HourSubcomponents[~Extended] TemporalSign ::: ASCIISign <MINUS> ASCIISign ::: one of + - Hour ::: 0 DecimalDigit 1 DecimalDigit 20 21 22 23 HourSubcomponents[Extended] ::: TimeSeparator[?Extended] MinuteSecond TimeSeparator[?Extended] MinuteSecond TimeSeparator[?Extended] MinuteSecond TemporalDecimalFractionopt TimeSeparator[Extended] ::: [+Extended] : [~Extended] [empty] MinuteSecond ::: 0 DecimalDigit 1 DecimalDigit 2 DecimalDigit 3 DecimalDigit 4 DecimalDigit 5 DecimalDigit TemporalDecimalFraction ::: TemporalDecimalSeparator DecimalDigit TemporalDecimalSeparator DecimalDigit DecimalDigit TemporalDecimalSeparator DecimalDigit DecimalDigit DecimalDigit TemporalDecimalSeparator DecimalDigit DecimalDigit DecimalDigit DecimalDigit TemporalDecimalSeparator DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit TemporalDecimalSeparator DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit TemporalDecimalSeparator DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit TemporalDecimalSeparator DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit TemporalDecimalSeparator DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit DecimalDigit TemporalDecimalSeparator ::: one of . ,

This function performs the following steps when called:

1. If NewTarget is undefined, then
   1. Let now be the time value (UTC) identifying the current time.
   2. Return ToDateString(now).
2. Let numberOfArgs be the number of elements in values.
3. If numberOfArgs = 0, then
   1. Let dv be the time value (UTC) identifying the current time.
4. Else if numberOfArgs = 1, then
   1. Let value be values[0].
   2. If value is an Object and value has a [[DateValue]] internal slot, then
      1. Let tv be ! thisTimeValue(value).
   3. Else,
      1. Let v be ? ToPrimitive(value).
      2. If v is a String, then
         1. Assert: The next step never returns an abrupt completion because v is a String.
         2. Let tv be the result of parsing v as a date, in exactly the same manner as for the parse method (21.4.3.2).
      3. Else,
         1. Let tv be ? ToNumber(v).
   4. Let dv be TimeClip(tv).
5. Else,
   1. Assert: numberOfArgs ≥ 2.
   2. Let y be ? ToNumber(values[0]).
   3. Let m be ? ToNumber(values[1]).
   4. If numberOfArgs > 2, let dt be ? ToNumber(values[2]); else let dt be 1_𝔽.
   5. If numberOfArgs > 3, let h be ? ToNumber(values[3]); else let h be +0_𝔽.
   6. If numberOfArgs > 4, let min be ? ToNumber(values[4]); else let min be +0_𝔽.
   7. If numberOfArgs > 5, let s be ? ToNumber(values[5]); else let s be +0_𝔽.
   8. If numberOfArgs > 6, let milli be ? ToNumber(values[6]); else let milli be +0_𝔽.
   9. If y is NaN, let yr be NaN.
   10. Else,
       1. Let yi be ! ToIntegerOrInfinity(y).
       2. If 0 ≤ yi ≤ 99, let yr be 1900_𝔽 + 𝔽(yi); otherwise, let yr be y.
   11. Let finalDate be MakeDate(MakeDay(yr, m, dt), MakeTime(h, min, s, milli)).
   12. Let dv be TimeClip(UTC(finalDate)).
6. Let O be ? OrdinaryCreateFromConstructor(NewTarget, "%Date.prototype%", « [[DateValue]] »).
7. Set O.[[DateValue]] to dv.
8. Return O.

This function returns the time value designating the UTC date and time of the occurrence of the call to it.

This function applies the ToString operator to its argument. If ToString results in an abrupt completion the Completion Record is immediately returned. Otherwise, this function interprets the resulting String as a date and time; it returns a Number, the UTC time value corresponding to the date and time. The String may be interpreted as a local time, a UTC time, or a time in some other time zone, depending on the contents of the String. The function first attempts to parse the String according to the format described in Date Time String Format (21.4.1.18), including expanded years. If the String does not conform to that format the function may fall back to any implementation-specific heuristics or implementation-specific date formats. Strings that are unrecognizable or contain out-of-bounds format element values shall cause this function to return NaN.

If the String conforms to the Date Time String Format, substitute values take the place of absent format elements. When the MM or DD elements are absent, "01" is used. When the HH, mm, or ss elements are absent, "00" is used. When the sss element is absent, "000" is used. When the UTC offset representation is absent, date-only forms are interpreted as a UTC time and date-time forms are interpreted as a local time.

If x is any Date whose milliseconds amount is zero within a particular implementation of ECMAScript, then all of the following expressions should produce the same numeric value in that implementation, if all the properties referenced have their initial values:

          x.valueOf()
          Date.parse(x.toString())
          Date.parse(x.toUTCString())
          Date.parse(x.toISOString())
        

However, the expression

          Date.parse(x.toLocaleString())
        

is not required to produce the same Number value as the preceding three expressions and, in general, the value produced by this function is implementation-defined when given any String value that does not conform to the Date Time String Format (21.4.1.18) and that could not be produced in that implementation by the toString or toUTCString method.

The initial value of Date.prototype is the Date prototype object.

This property has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: false }.

This function performs the following steps when called:

1. Let y be ? ToNumber(year).
2. If month is present, let m be ? ToNumber(month); else let m be +0_𝔽.
3. If date is present, let dt be ? ToNumber(date); else let dt be 1_𝔽.
4. If hours is present, let h be ? ToNumber(hours); else let h be +0_𝔽.
5. If minutes is present, let min be ? ToNumber(minutes); else let min be +0_𝔽.
6. If seconds is present, let s be ? ToNumber(seconds); else let s be +0_𝔽.
7. If ms is present, let milli be ? ToNumber(ms); else let milli be +0_𝔽.
8. If y is NaN, let yr be NaN.
9. Else,
   1. Let yi be ! ToIntegerOrInfinity(y).
   2. If 0 ≤ yi ≤ 99, let yr be 1900_𝔽 + 𝔽(yi); otherwise, let yr be y.
10. Return TimeClip(MakeDate(MakeDay(yr, m, dt), MakeTime(h, min, s, milli))).

The "length" property of this function is 7_𝔽.

Note

This function differs from the Date constructor in two ways: it returns a time value as a Number, rather than creating a Date, and it interprets the arguments in UTC rather than as local time.

The initial value of Date.prototype.constructor is %Date%.

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return DateFromTime(LocalTime(t)).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return WeekDay(LocalTime(t)).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return YearFromTime(LocalTime(t)).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return HourFromTime(LocalTime(t)).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return msFromTime(LocalTime(t)).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return MinFromTime(LocalTime(t)).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return MonthFromTime(LocalTime(t)).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return SecFromTime(LocalTime(t)).

This method performs the following steps when called:

1. Return ? thisTimeValue(this value).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return (t - LocalTime(t)) / msPerMinute.

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return DateFromTime(t).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return WeekDay(t).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return YearFromTime(t).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return HourFromTime(t).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return msFromTime(t).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return MinFromTime(t).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return MonthFromTime(t).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, return NaN.
3. Return SecFromTime(t).

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let dt be ? ToNumber(date).
3. If t is NaN, return NaN.
4. Set t to LocalTime(t).
5. Let newDate be MakeDate(MakeDay(YearFromTime(t), MonthFromTime(t), dt), TimeWithinDay(t)).
6. Let u be TimeClip(UTC(newDate)).
7. Set the [[DateValue]] internal slot of this Date object to u.
8. Return u.

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let y be ? ToNumber(year).
3. If t is NaN, set t to +0_𝔽; otherwise, set t to LocalTime(t).
4. If month is not present, let m be MonthFromTime(t); otherwise, let m be ? ToNumber(month).
5. If date is not present, let dt be DateFromTime(t); otherwise, let dt be ? ToNumber(date).
6. Let newDate be MakeDate(MakeDay(y, m, dt), TimeWithinDay(t)).
7. Let u be TimeClip(UTC(newDate)).
8. Set the [[DateValue]] internal slot of this Date object to u.
9. Return u.

The "length" property of this method is 3_𝔽.

Note

If month is not present, this method behaves as if month was present with the value getMonth(). If date is not present, it behaves as if date was present with the value getDate().

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let h be ? ToNumber(hour).
3. If min is present, let m be ? ToNumber(min).
4. If sec is present, let s be ? ToNumber(sec).
5. If ms is present, let milli be ? ToNumber(ms).
6. If t is NaN, return NaN.
7. Set t to LocalTime(t).
8. If min is not present, let m be MinFromTime(t).
9. If sec is not present, let s be SecFromTime(t).
10. If ms is not present, let milli be msFromTime(t).
11. Let date be MakeDate(Day(t), MakeTime(h, m, s, milli)).
12. Let u be TimeClip(UTC(date)).
13. Set the [[DateValue]] internal slot of this Date object to u.
14. Return u.

The "length" property of this method is 4_𝔽.

Note

If min is not present, this method behaves as if min was present with the value getMinutes(). If sec is not present, it behaves as if sec was present with the value getSeconds(). If ms is not present, it behaves as if ms was present with the value getMilliseconds().

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Set ms to ? ToNumber(ms).
3. If t is NaN, return NaN.
4. Set t to LocalTime(t).
5. Let time be MakeTime(HourFromTime(t), MinFromTime(t), SecFromTime(t), ms).
6. Let u be TimeClip(UTC(MakeDate(Day(t), time))).
7. Set the [[DateValue]] internal slot of this Date object to u.
8. Return u.

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let m be ? ToNumber(min).
3. If sec is present, let s be ? ToNumber(sec).
4. If ms is present, let milli be ? ToNumber(ms).
5. If t is NaN, return NaN.
6. Set t to LocalTime(t).
7. If sec is not present, let s be SecFromTime(t).
8. If ms is not present, let milli be msFromTime(t).
9. Let date be MakeDate(Day(t), MakeTime(HourFromTime(t), m, s, milli)).
10. Let u be TimeClip(UTC(date)).
11. Set the [[DateValue]] internal slot of this Date object to u.
12. Return u.

The "length" property of this method is 3_𝔽.

Note

If sec is not present, this method behaves as if sec was present with the value getSeconds(). If ms is not present, this behaves as if ms was present with the value getMilliseconds().

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let m be ? ToNumber(month).
3. If date is present, let dt be ? ToNumber(date).
4. If t is NaN, return NaN.
5. Set t to LocalTime(t).
6. If date is not present, let dt be DateFromTime(t).
7. Let newDate be MakeDate(MakeDay(YearFromTime(t), m, dt), TimeWithinDay(t)).
8. Let u be TimeClip(UTC(newDate)).
9. Set the [[DateValue]] internal slot of this Date object to u.
10. Return u.

The "length" property of this method is 2_𝔽.

Note

If date is not present, this method behaves as if date was present with the value getDate().

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let s be ? ToNumber(sec).
3. If ms is present, let milli be ? ToNumber(ms).
4. If t is NaN, return NaN.
5. Set t to LocalTime(t).
6. If ms is not present, let milli be msFromTime(t).
7. Let date be MakeDate(Day(t), MakeTime(HourFromTime(t), MinFromTime(t), s, milli)).
8. Let u be TimeClip(UTC(date)).
9. Set the [[DateValue]] internal slot of this Date object to u.
10. Return u.

The "length" property of this method is 2_𝔽.

Note

If ms is not present, this method behaves as if ms was present with the value getMilliseconds().

This method performs the following steps when called:

1. Perform ? thisTimeValue(this value).
2. Let t be ? ToNumber(time).
3. Let v be TimeClip(t).
4. Set the [[DateValue]] internal slot of this Date object to v.
5. Return v.

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let dt be ? ToNumber(date).
3. If t is NaN, return NaN.
4. Let newDate be MakeDate(MakeDay(YearFromTime(t), MonthFromTime(t), dt), TimeWithinDay(t)).
5. Let v be TimeClip(newDate).
6. Set the [[DateValue]] internal slot of this Date object to v.
7. Return v.

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. If t is NaN, set t to +0_𝔽.
3. Let y be ? ToNumber(year).
4. If month is not present, let m be MonthFromTime(t); otherwise, let m be ? ToNumber(month).
5. If date is not present, let dt be DateFromTime(t); otherwise, let dt be ? ToNumber(date).
6. Let newDate be MakeDate(MakeDay(y, m, dt), TimeWithinDay(t)).
7. Let v be TimeClip(newDate).
8. Set the [[DateValue]] internal slot of this Date object to v.
9. Return v.

The "length" property of this method is 3_𝔽.

Note

If month is not present, this method behaves as if month was present with the value getUTCMonth(). If date is not present, it behaves as if date was present with the value getUTCDate().

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let h be ? ToNumber(hour).
3. If min is present, let m be ? ToNumber(min).
4. If sec is present, let s be ? ToNumber(sec).
5. If ms is present, let milli be ? ToNumber(ms).
6. If t is NaN, return NaN.
7. If min is not present, let m be MinFromTime(t).
8. If sec is not present, let s be SecFromTime(t).
9. If ms is not present, let milli be msFromTime(t).
10. Let date be MakeDate(Day(t), MakeTime(h, m, s, milli)).
11. Let v be TimeClip(date).
12. Set the [[DateValue]] internal slot of this Date object to v.
13. Return v.

The "length" property of this method is 4_𝔽.

Note

If min is not present, this method behaves as if min was present with the value getUTCMinutes(). If sec is not present, it behaves as if sec was present with the value getUTCSeconds(). If ms is not present, it behaves as if ms was present with the value getUTCMilliseconds().

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Set ms to ? ToNumber(ms).
3. If t is NaN, return NaN.
4. Let time be MakeTime(HourFromTime(t), MinFromTime(t), SecFromTime(t), ms).
5. Let v be TimeClip(MakeDate(Day(t), time)).
6. Set the [[DateValue]] internal slot of this Date object to v.
7. Return v.

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let m be ? ToNumber(min).
3. If sec is present, let s be ? ToNumber(sec).
4. If ms is present, let milli be ? ToNumber(ms).
5. If t is NaN, return NaN.
6. If sec is not present, let s be SecFromTime(t).
7. If ms is not present, let milli be msFromTime(t).
8. Let date be MakeDate(Day(t), MakeTime(HourFromTime(t), m, s, milli)).
9. Let v be TimeClip(date).
10. Set the [[DateValue]] internal slot of this Date object to v.
11. Return v.

The "length" property of this method is 3_𝔽.

Note

If sec is not present, this method behaves as if sec was present with the value getUTCSeconds(). If ms is not present, it behaves as if ms was present with the value return by getUTCMilliseconds().

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let m be ? ToNumber(month).
3. If date is present, let dt be ? ToNumber(date).
4. If t is NaN, return NaN.
5. If date is not present, let dt be DateFromTime(t).
6. Let newDate be MakeDate(MakeDay(YearFromTime(t), m, dt), TimeWithinDay(t)).
7. Let v be TimeClip(newDate).
8. Set the [[DateValue]] internal slot of this Date object to v.
9. Return v.

The "length" property of this method is 2_𝔽.

Note

If date is not present, this method behaves as if date was present with the value getUTCDate().

This method performs the following steps when called:

1. Let t be ? thisTimeValue(this value).
2. Let s be ? ToNumber(sec).
3. If ms is present, let milli be ? ToNumber(ms).
4. If t is NaN, return NaN.
5. If ms is not present, let milli be msFromTime(t).
6. Let date be MakeDate(Day(t), MakeTime(HourFromTime(t), MinFromTime(t), s, milli)).
7. Let v be TimeClip(date).
8. Set the [[DateValue]] internal slot of this Date object to v.
9. Return v.

The "length" property of this method is 2_𝔽.

Note

If ms is not present, this method behaves as if ms was present with the value getUTCMilliseconds().

This method performs the following steps when called:

1. Let O be this Date object.
2. Let tv be ? thisTimeValue(O).
3. If tv is NaN, return "Invalid Date".
4. Let t be LocalTime(tv).
5. Return DateString(t).

If this time value is not a finite Number or if it corresponds with a year that cannot be represented in the Date Time String Format, this method throws a RangeError exception. Otherwise, it returns a String representation of this time value in that format on the UTC time scale, including all format elements and the UTC offset representation "Z".

This method provides a String representation of a Date for use by JSON.stringify (25.5.2).

It performs the following steps when called:

1. Let O be ? ToObject(this value).
2. Let tv be ? ToPrimitive(O, number).
3. If tv is a Number and tv is not finite, return null.
4. Return ? Invoke(O, "toISOString").

Note 1

The argument is ignored.

Note 2

This method is intentionally generic; it does not require that its this value be a Date. Therefore, it can be transferred to other kinds of objects for use as a method. However, it does require that any such object have a toISOString method.

An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement this method as specified in the ECMA-402 specification. If an ECMAScript implementation does not include the ECMA-402 API the following specification of this method is used:

This method returns a String value. The contents of the String are implementation-defined, but are intended to represent the “date” portion of the Date in the current time zone in a convenient, human-readable form that corresponds to the conventions of the host environment's current locale.

The meaning of the optional parameters to this method are defined in the ECMA-402 specification; implementations that do not include ECMA-402 support must not use those parameter positions for anything else.

An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement this method as specified in the ECMA-402 specification. If an ECMAScript implementation does not include the ECMA-402 API the following specification of this method is used:

This method returns a String value. The contents of the String are implementation-defined, but are intended to represent the Date in the current time zone in a convenient, human-readable form that corresponds to the conventions of the host environment's current locale.

The meaning of the optional parameters to this method are defined in the ECMA-402 specification; implementations that do not include ECMA-402 support must not use those parameter positions for anything else.

An ECMAScript implementation that includes the ECMA-402 Internationalization API must implement this method as specified in the ECMA-402 specification. If an ECMAScript implementation does not include the ECMA-402 API the following specification of this method is used:

This method returns a String value. The contents of the String are implementation-defined, but are intended to represent the “time” portion of the Date in the current time zone in a convenient, human-readable form that corresponds to the conventions of the host environment's current locale.

The meaning of the optional parameters to this method are defined in the ECMA-402 specification; implementations that do not include ECMA-402 support must not use those parameter positions for anything else.

This method performs the following steps when called:

1. Let tv be ? thisTimeValue(this value).
2. Return ToDateString(tv).

Note 1

For any Date d such that d.[[DateValue]] is evenly divisible by 1000, the result of Date.parse(d.toString()) = d.valueOf(). See 21.4.3.2.

Note 2

This method is not generic; it throws a TypeError exception if its this value is not a Date. Therefore, it cannot be transferred to other kinds of objects for use as a method.