Google tried to do that with Dart, and failed. In fairness Dart 1 was much worse than Dart 2… So maybe that was a good thing because there’s no way they’d have been able to improve Dart as much as they have if it was part of the web.

For dates there finally is something better anyway: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal