Deno has had it behind the `--untable-temporal` flag for quite a few Minor versions now and the latest Minor update (because of TC-39's Stage 4 acceptance and V8 itself also marking the API as Stable) removed the requirement for the flag and it is out of the box.

Node 26! Only a matter of time... :)

FWIW, I've been using it server-side via the js-temporal polyfill for some time, no issues.

Try `node --harmony-temporal`