The toString() method of Temporal.Instant instances returns a string representing this instant in the RFC 9557 format using the specified time zone.

Syntax

toString()
toString(options)

Parameters

options Optional

An object containing some or all of the following properties (in the order they are retrieved and validated):

fractionalSecondDigits Optional

Either an integer from 0 to 9, or the string "auto". The default is "auto". If "auto", then trailing zeros are removed from the fractional seconds. Otherwise, the fractional part of the second component contains this many digits, padded with zeros or rounded as necessary.

roundingMode Optional

A string specifying how to round off fractional second digits beyond fractionalSecondDigits. See Intl.NumberFormat(). Defaults to "trunc".

smallestUnit Optional

A string specifying the smallest unit to include in the output. Possible values are "minute", "second", "millisecond", "microsecond", and "nanosecond", or their plural forms, which (except "minute") are equivalent to fractionalSecondDigits values of 0, 3, 6, 9, respectively. If specified, then fractionalSecondDigits is ignored.

timeZone Optional

Either a string or a Temporal.ZonedDateTime instance representing the time zone to use. If a Temporal.ZonedDateTime instance, its time zone is used. If a string, it can be a named time zone identifier, an offset time zone identifier, or a date-time string containing a time zone identifier or an offset (see time zones and offsets for more information). Defaults to "UTC".

Return value

A string in the RFC 9557 format representing this instant using the specified time zone. No annotations, such as time zone names, are included.

Exceptions

RangeError

Thrown if any of the options is invalid.

Examples

Using toString()

const instant = Temporal.Instant.fromEpochMilliseconds(1627814412345);
console.log(instant.toString()); // '2021-08-01T10:40:12.345Z'

// Stringification implicitly calls toString()
console.log(`${instant}`); // '2021-08-01T10:40:12.345Z'

Using options

const instant = Temporal.Instant.fromEpochMilliseconds(1627814412345);
console.log(instant.toString({ fractionalSecondDigits: 1 })); // '2021-08-01T10:40:12.3Z'
console.log(instant.toString({ smallestUnit: "minute" })); // '2021-08-01T10:40Z'
console.log(instant.toString({ timeZone: "America/New_York" })); // '2021-08-01T06:40:12.345-04:00'

// The time zone name automatically resolves to the correct offset
// based on the instant; for example, America/New_York is UTC-4 in summer,
// but UTC-5 in winter.
const instant2 = Temporal.Instant.fromEpochMilliseconds(1577836800000);
console.log(instant2.toString({ timeZone: "UTC" })); // '2029-12-31T23:00:00Z'
console.log(instant2.toString({ timeZone: "America/New_York" })); // '2019-12-31T19:00:00-05:00'

Specifications

Browser compatibility

See also

• Temporal.Instant
• Temporal.Instant.from()
• Temporal.Instant.prototype.toJSON()
• Temporal.Instant.prototype.toLocaleString()