Datetime format

[andrw3000]

For messages.timestamp we are specifying a datetime object. Which format shall we adopt?

E.g. datetime.datetime.now().isoformat()?

[JDonaldM]

I'm happy to go with ISO but I think Pydantic offers some flexibility.
From the Pydantic docs on datetime validation:

• datetime fields will accept values of type:
• datetime; an existing datetime object
• int or float; assumed as Unix time, i.e. seconds (if >= -2e10 and <= 2e10) or milliseconds (if < -2e10or > 2e10) since 1 January 1970
• str; the following formats are accepted:
  • YYYY-MM-DD[T]HH:MM[:SS[.ffffff]][Z or [±]HH[:]MM]
  • int or float as a string (assumed as Unix time)