Support for RFC 3339 in target time zone

[bsidhom]

I'm not able to get times to print in RFC 3339 using the format_datetime function:

>>> get_local_timezone()

  get_local_timezone()

    = America/Los_Angeles    [String]

>>> format_datetime("%Y-%m-%dT%H:%M:%S%:z", local(now()))

  format_datetime("%Y-%m-%dT%H:%M:%S%:z", local(now()))

    = 2024-02-23T22:01:52+00:00    [String]

>>> now()

  now()

    = Fri, 23 Feb 2024 14:01:54 -0800    [DateTime]

According to the chrono docs, %z and friends should give the local offset relative to UTC. However, it looks like the TZ info is getting dropped before being sent to the formatter and it's always displaying in UTC. (I would also like to add formatters/parsers for the reference format to the prelude, but I'm not sure if others would find that useful.)

[bsidhom]

Sorry, looks like parsing already works as expected via the datetime function. So it’s only formatting that’s currently broken.

[sharkdp]

Thank you for reporting this. I believe I have a fix in #378, but it needs some testing.

[sharkdp]

Also, there's no need to do now() -> local or local(now()). now() will return a datetime in the local timezone.

[bsidhom]

Yeah, I tried that first but noted that it displayed in UTC. Didn’t realize that was unexpected behavior.

[sharkdp]

For datetime(…), do we want to return the datetime object in the specified timezone (current behavior in #378), or in the local timezone (current behavior on master)?

[bsidhom]

I think it’s best to return the specified TZ offset for consistency. Users can always convert to local after parsing, but it’s otherwise difficult to recover the original offset.

[sharkdp]

This should now be fixed: https://numbat.dev/?q=format_datetime%28%22%25Y-%25m-%25dT%25H%3A%25M%3A%25S%25%3Az%22%2C+now%28%29%29%E2%8F%8E