timedelta additions to pendulum.DateTime

[andreivnegrean]

• I am on the latest Pendulum version.

• I have searched the issues of this repo and believe that this is not a duplicate.

• OS version and name: macOS 13.2.1 (22D68)

• Pendulum version: 3.0.0

Issue

Hi,

It seems like pendulum.DateTime additions of timedelta don't give the same result as in the case of pendulum.Duration additions when crossing a DST timezone boundary.

Examples:

assert DateTime(year=2024, month=11, day=3, hour=1, tzinfo=Timezone("America/Los_Angeles")) + timedelta(days=30) == DateTime(year=2024, month=12, day=3, hour=1, tzinfo=Timezone("America/Los_Angeles"))

throws the following:

AssertionError: assert DateTime(2024, 12, 3, 0, 0, 0, tzinfo=Timezone('America/Los_Angeles')) == DateTime(2024, 12, 3, 1, 0, 0, tzinfo=Timezone('America/Los_Angeles'))

the same assertion passes if adding a Duration instead of timedelta:

assert DateTime(year=2024, month=11, day=3, hour=1, tzinfo=Timezone("America/Los_Angeles")) + Duration(months=1) == DateTime(year=2024, month=12, day=3, hour=1, tzinfo=Timezone("America/Los_Angeles"))

The issue is also reproducible when adding weeks:

assert DateTime(year=2024, month=11, day=3, hour=1, tzinfo=Timezone("America/Los_Angeles")) + timedelta(weeks=1) == DateTime(year=2024, month=11, day=10, hour=1, tzinfo=Timezone("America/Los_Angeles"))

[ariebovenberg]

I'm assuming this is because months in Duration is counted on the calendar (1am one month later is still 1am), while days in timedelta considers days to always be 24 hours (1am + 30×24h may not result in 1am again due to DST transitions).