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  2. JavaScript
  3. Reference
  4. Standard built-in objects
  5. Temporal
  6. Temporal.PlainDate
  7. since()

Temporal.PlainDate.prototype.since()

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The since() method of Temporal.PlainDate instances returns a new Temporal.Duration object representing the duration from another date (in a form convertible by Temporal.PlainDate.from()) to this date. The duration is positive if the other date is before this date, and negative if after.

This method does this - other. To do other - this, use the until() method.

Syntax

js
since(other)
since(other, options)

Parameters

other

A string, an object, or a Temporal.PlainDate instance representing a date to subtract from this date. It is converted to a Temporal.PlainDate object using the same algorithm as Temporal.PlainDate.from(). It must have the same calendar as this.

options Optional

An object containing the options for Temporal.Duration.prototype.round(), which includes largestUnit, roundingIncrement, roundingMode, and smallestUnit. largestUnit and smallestUnit only accept the units: "years", "months", "weeks", "days", or their singular forms. For largestUnit, the default value "auto" means "days" or smallestUnit, whichever is greater. For smallestUnit, the default value is "days". The current date is used as the relativeTo option. Note that using units larger than "days" may make the duration not portable to other calendars or dates.

Return value

A new Temporal.Duration object representing the duration since other to this date. The duration is positive if other is before this date, and negative if after.

Exceptions

RangeError

Thrown in one of the following cases:

  • other has a different calendar than this.
  • Any of the options is invalid.

Examples

Using since()

js
const date = Temporal.PlainDate.from("2022-12-25");
const now = Temporal.Now.plainDateISO();
const duration = now.since(date);
const formatter = new Intl.DurationFormat("en-US", { style: "long" });
console.log(`It's been ${formatter.format(duration)} since that Christmas...`);
// Expected output: "It's been [number] days since that Christmas..."

const duration2 = now.since(date, { smallestUnit: "months" });
console.log(`It's been ${formatter.format(duration2)} since that Christmas...`);
// Expected output: "It's been [number] months since that Christmas..."

const duration3 = now.since(date, {
  largestUnit: "years",
  smallestUnit: "months",
});
console.log(`It's been ${formatter.format(duration3)} since that Christmas...`);
// Expected output: "It's been [number] years, [number] months since that Christmas..."

Rounding the result

By default the fractional part of the smallestUnit is truncated. You can round it up using the roundingIncrement and roundingMode options.

js
const date1 = Temporal.PlainDate.from("2022-01-01");
const date2 = Temporal.PlainDate.from("2022-01-28");
const duration = date2.since(date1, {
  smallestUnit: "days",
  roundingIncrement: 5,
  roundingMode: "ceil",
});
console.log(duration.toString()); // "P30D"

Comparing different calendars

By default, the two dates must have the same calendar. This is to avoid ambiguity in the meaning of months and years. If you want to compare dates from different calendars, you can convert them to the same calendar first.

js
const date1 = Temporal.PlainDate.from("2022-01-01");
const date2 = Temporal.PlainDate.from("2022-01-28[u-ca=chinese]");
const duration = date2.withCalendar("iso8601").since(date1);
console.log(duration.toString()); // "P27D"

Specifications

Specification
Temporal
# sec-temporal.plaindate.prototype.since

Browser compatibility

See also

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