Support `temporal` TC39 proposal

[SimenB]

• FakeTimers version : 6.0.1
• Environment : N/A
• Example URL : N/A
• Other libraries you are using: None

Repo: https://github.com/tc39/proposal-temporal/

We should support faking out usage of all Temporal.now.* methods. Not sure if we need to fake anything else?

Note that I do not think we should support Temporal now - the proposal is still at stage 2. So consider this more of a tracking issue than something that's actionable right now.

What did you expect to happen?
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What actually happens
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How to reproduce
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[benjamingr]

Cc @littledan I remember you asking for feedback on Temporal.

Is there anything other than .now that sinon would need to fake?

[SimenB]

It's now stage 3: tc39/proposal-temporal#1440. 🎉 Is this a good time to add support? Along with some docs caveat that it's still unstable (and of course not added to toFake by default). Or should we wait for one engine to land it?

[benjamingr]

When does it land in Chrome?

[SimenB]

I have exactly zero clue 😅

[ljharb]

It is stage 3, but will not be shipped unflagged at this time, so it'll be awhile.

You will only have to mock out Temporal.now, by design.

I would start implementing now, but perhaps hold off shipping it until at least one engine has landed it, or at least until a production-ready spec-compliant polyfill exists.

[SimenB]

You will only have to mock out Temporal.now, by design.

Wonderful 👍

I would start implementing now, but perhaps hold off shipping it until at least one engine has landed it, or at least until a production-ready spec-compliant polyfill exists.

If somebody is up for implementing it, I think we can also ship it as long as it's clearly marked as unstable in docs and possibly code, e.g. unstable_enableTemporalSupport: boolean or something. Not sure, and I don't feel strongly

[fatso83]

Still Stage 3. Not implemented by any browsers, yet.

EDIT: still seeing commits as of December 11, 2024

[EmilyRagan]

Still stage 3, but now available in Firefox, and there is a polyfill for it. I'm starting to use this polyfill, and it seems like perhaps useFakeTimers does work with Temporal.Now at this point

[fatso83]

After 9 years, this has reached Stage 4 and is shipping in Chrome and Firefox. It's time to do this. Any takers? 😁

from the TC repo

---

This proposal is currently Stage 4.

It will be merged into the tc39/ecma262#3759 and tc39/ecma402#1044 standards and this repository will be archived.

Implementation status:

SpiderMonkey/Firefox: shipped in Firefox 139 (on 2025-05-27)
V8/Chrome: shipped in Chrome 144 (on 2026-01-13)
nodejs/node#57127
JavaScriptCore/Safari
boa-dev/boa#1804
oracle/graaljs#851: planned to ship in GraalVM 25.1.0
Kiesel
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