What format is expected by the API when working with `datetime` fields?

What format is expected by the API when working with `datetime` fields?

Hi there - I'm trying to update records via the API (v2) and am getting errors when trying to send a datetime field.

I've tried a regular Javascript date object, an ISO string, a UTC string, and a 'd/m/y' formatted date string.

I've looked at the documentation and can see no information about the different field types anywhere.

Please advise.

Thanks,

Chirpy.