The add() method of Temporal.Instant instances returns a new Temporal.Instant object representing this instant moved forward by a given duration (in a form convertible by Temporal.Duration.from()).

Syntax

add(duration)

Parameters

duration

A string, an object, or a Temporal.Duration instance representing a duration to add to this instant. It is converted to a Temporal.Duration object using the same algorithm as Temporal.Duration.from().

Return value

A new Temporal.Instant object representing adding duration to this instant. If duration is positive, then the returned instant is later than this instant; if duration is negative, then the returned instant is earlier than this instant.

Exceptions

RangeError

Thrown in one of the following cases:

• duration is a calendar duration (it has a non-zero years, months, or weeks), or has a non-zero days, because calendar durations are ambiguous without a calendar and time reference.
• The result is not in the representable range, which is ±10⁸ days, or about ±273,972.6 years, from the Unix epoch.

Description

In essence, the add() method first gets the number of nanoseconds represented by duration, adds it to this instant's epochNanoseconds, and then creates a new Temporal.Instant object from the result. Therefore, the duration must unambiguously represent a fixed amount of time.

If you want to add a calendar duration, the addition must be performed in the context of a calendar and a time zone to account for the variable lengths of months, years, and days (because of daylight saving time). In this case, convert the instant to a Temporal.ZonedDateTime object, add the duration, and then convert the result back to an instant.

Adding a duration is equivalent to subtracting its negation.

Examples

Adding a Temporal.Duration

const instant = Temporal.Instant.fromEpochMilliseconds(0);
const duration = Temporal.Duration.from("PT1S");
const newInstant = instant.add(duration);
console.log(newInstant.epochMilliseconds); // 1000

Adding an object or a string

const instant = Temporal.Instant.fromEpochMilliseconds(0);
const newInstant = instant.add({ seconds: 1 });
console.log(newInstant.epochMilliseconds); // 1000

const newInstant2 = instant.add("PT1S");
console.log(newInstant2.epochMilliseconds); // 1000

Adding a calendar duration

const instant = Temporal.Instant.fromEpochMilliseconds(1730610000000);
const duration = Temporal.Duration.from({ days: 1 });

// This instant is 2024-11-03T01:00:00-04:00[America/New_York],
// which is a DST transition day in the US.
const instant2 = instant
  .toZonedDateTimeISO("America/New_York")
  .add(duration)
  .toInstant();
console.log(instant2.epochMilliseconds); // 1730700000000

// The same instant is not a DST transition day in Paris.
const instant3 = instant
  .toZonedDateTimeISO("Europe/Paris")
  .add(duration)
  .toInstant();
console.log(instant3.epochMilliseconds); // 1730696400000

Specifications

Browser compatibility

See also

• Temporal.Instant
• Temporal.Duration
• Temporal.Instant.prototype.subtract()