Fix `datetime` serialization for non-UTC timestamps

[StabbarN]

How do you use Sentry?

Sentry Saas (sentry.io)

Version

2.13.0

Steps to Reproduce

The events at https://xyz.sentry.io/issues/123/events/abc/ lose datetimes' timezone.

Expected Result

The following code with .isoformat()

from zoneinfo import ZoneInfo
sthlm = datetime.datetime(2024, 3, 1, tzinfo=ZoneInfo("Europe/Stockholm"))
new_york = datetime.datetime(2024, 3, 1, tzinfo=ZoneInfo("America/New_York"))
sentry_sdk.set_context(
    "extra_context",
    {
        "sthlm": sthlm.isoformat(),
        "new_york": new_york.isoformat(),
    },
)
Hub.current.capture_event(...)

results in the screenshot below

Actual Result

The following code

from zoneinfo import ZoneInfo
sthlm = datetime.datetime(2024, 3, 1, tzinfo=ZoneInfo("Europe/Stockholm"))
new_york = datetime.datetime(2024, 3, 1, tzinfo=ZoneInfo("America/New_York"))
sentry_sdk.set_context(
    "extra_context",
    {
        "sthlm": sthlm,
        "new_york": new_york,
    },
)
Hub.current.capture_event(...)

will lose timezone. See screenshot below

[szokeasaurusrex]

@StabbarN, looks like this happening because of how we serialize datetime objects appearing in an event payload. The serialization is performed here:

sentry-python/sentry_sdk/serializer.py

Lines 296 to 301 in 269d96d

	elif isinstance(obj, datetime):
	return (
	str(format_timestamp(obj))
	if not should_repr_strings
	else _safe_repr_wrapper(obj)
	)

The above code is calling the following format_timestamp function to format the datetime object; as you can see, the timezone is excluded here:

sentry-python/sentry_sdk/utils.py

Lines 228 to 230 in 269d96d

	def format_timestamp(value):
	# type: (datetime) -> str
	return value.strftime("%Y-%m-%dT%H:%M:%S.%fZ")

Given that this logic is used to serialize all dates in an event payload, and given that the code seems to have remained relatively unchanged for quite some time (5+ years), I would be somewhat reluctant to change the serialization logic here unless absolutely necessary.

As you already demonstrated in the "Expected Result" section, you can work around this issue by manually formatting the datetime object using .isoformat(), so I would recommend just using .isoformat() when sending the date. Generally, if you have specific formatting needs for any additional data sent on an event, it is best to format the data yourself before setting the data on the event; otherwise, you are relying on our serialization logic which might produce different results from what you would desire.

Is there any reason preventing you from simply using .isoformat()?

[StabbarN]

Thanks for the explaination and links.

Is there any reason preventing you from simply using .isoformat()?

It's not a problem for us anymore, but it may be for other users tho. Stripping timezone is a bit nasty.
We recursively parse extra_context and use .isoformat() if the value is a datetime.