ecerulm commented on pull request #16631:
URL: https://github.com/apache/airflow/pull/16631#issuecomment-867612620
Just for clarification,
The whole `pendulum.tz.timezone.xxx` behaviour is a bit confusing. The
current codebase assumes that if you get a timezone "name" (with `.name`) you
can reconstruct a `datetime.tzinfo` with `pendulum.timezone(that_name)` which
is **only** true in certain conditions...
* for **many** "named" timezones like `UTC`, `Europe/Stockholm`, `CET`,etc
this holds true and that's what people had to use before in airflow.
* for all offset timezones like `+01:00`, etc this is **not true** and it
will raise `InvalidTimezone`
Besides that, there are some other pendulum/`datetime.tzinfo` oddities that
prevent some simplications.
* you can't just use `.tzname()`, because you need an actual datetime in
addition to the timezone to get the name.
* even if you just took the dag.start_date + dag.timezone (or the
dag.start_date.tzinfo), `tzname()` can give back a named timezone like CEST
that cannot be converted back to an actual `datetime.tzinfo` object by
`pendulum.timezone`) .
```
start_date = pendulum.datetime(2021,1,1,tzinfo=timezone.utc) # as dag
start_date is converted to utc
timezone = pendulum.timezone("Europe/Stockholm") # dag.timezone keeps the
"original" timezone that came in the start_date argument to the constructor
timezone.tzname(start_date) # returns 'CEST'
pendulum.timezone(timezone.tzname(start_date)) # raises InvalidTimezone
```
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