Native Temporal and GMT

GMT is built on @js-temporal/polyfill, so it runs on a runtime that has no native Temporal. This page lists where Temporal is native and which GMT function matches each Temporal call.

Where Temporal runs

Checked 2026-10-26, from the MDN browser compatibility data.

Runtime	First version with Temporal
Chrome and Edge	144
Firefox	139
Node.js	26
Deno	2.7
Bun	1.4.0
Safari on macOS	Technology Preview only
Safari on iOS	not supported

Status of the specification

TC39 moved Temporal to Stage 4 on 2026-03-11. It is not yet part of ECMA-262. On 2026-10-26 the pull request that adds it, ecma262 #3966, was open. An earlier pull request, #3759, was closed without merging. The text of the proposal is at tc39.es/proposal-temporal, and the clause numbers below refer to it.

Temporal call to GMT function

Task	Temporal	GMT	Specification
Today in a zone	`Temporal.Now.plainDateISO(z).toString()`	`getZonedToday`	2.2.5
Now in a zone	`Temporal.Now.zonedDateTimeISO(z).toString()`	`getZonedNow`	2.2.4
Now as UTC	`Temporal.Now.instant().toString()`	`getUtcNow`	2.2.2
Add a month	`PlainDate.from(s).add({ months: 1 }).toString()`	`addDate`	3.3.21, 3.5.7
Add a calendar day in a zone	`ZonedDateTime.from(s).add({ days: 1 })`	`addZoned`	6.3.35, 6.5.5
Difference	`a.until(b, { largestUnit: "months" })`	`diffDate`	3.3.25, 12.3.9
Start of day	`zdt.startOfDay()`	`startOfZoned`	6.3.45, 11.1.14
Hours in a day	`zdt.hoursInDay`	`getHoursInZonedDay`	6.3.23
Change zone	`zdt.withTimeZone(z)`	`convertZonedToZoned`	6.3.33
UTC to zone	`Instant.from(u).toZonedDateTimeISO(z)`	`convertUtcToZoned`	8.3.15
Wall time to zone	`PlainDateTime.from(l).toZonedDateTime(z, { disambiguation })`	`convertPlainDateTimeToZoned`	5.3.38, 11.1.11
Does the wall time exist	No public method; the specification counts the candidate instants	`classifyLocal`	11.1.13
Next transition	`zdt.getTimeZoneTransition("next")`	`getDstTransitions`	6.3.46
Round	`zdt.round({ smallestUnit: "hour" })`	`roundZoned`	6.3.39
Equal values	`a.equals(b)`	`areZonedEqual`	6.3.40
ISO week	`d.yearOfWeek`, `d.weekOfYear`, `d.dayOfWeek`	`getIsoWeekDate`	3.3.12, 3.3.13, 12.3.18
Change calendar	`d.withCalendar("japanese")`	`convertDateToCalendar`	3.3.24
A year and a month	`PlainYearMonth.from(s).toString()`	`parseYearMonth`, `isValidYearMonth`	9.2.2
A month and a day	`PlainMonthDay.from(s).toString()`	`parseMonthDay`, `isValidMonthDay`	10.2.2
A month-day in a year	`md.toPlainDate({ year })`	`monthDayToDate`	10.3.12
Duration total	`Duration.from(s).total({ unit, relativeTo })`	`totalDuration`	7.3.21
A `Date` object	`date.toTemporalInstant()`	`toTemporalInstant`	14.9.1

The clause in each row is the rule GMT follows for that call.

Using both from one import

GMT re-exports Temporal, Intl and toTemporalInstant from its root, taken from the polyfill. Code that needs a Temporal object and a GMT function can take both from @northguild/gmt.

import { Temporal, toTemporalInstant } from "@northguild/gmt";

For the results other libraries return on the same inputs, see Behaviour of date libraries against Temporal. Each library has its own page: date-fns, Luxon, Day.js, Moment.js and @internationalized/date.