Pandas ENH: tz_convert with non-hour shifts from UTC

Feature Type

[X] Adding new functionality to pandas
[X] Changing existing functionality in pandas
[ ] Removing existing functionality in pandas

Problem Description

I would like to use tz_convert to be able to convert from local time (some timestamps with daylight savings) to standard time (no timestamps with daylight savings) in locations which employ 30 and 45 minute shifts from UTC time.

Currently my understanding is that tz_convert uses pytz. pytz.all_timezones does not include any timezones with 30 or 45 minute shifts, so this may be a feature request for pytz.

https://www.timeanddate.com/time/time-zones-interesting.html

Feature Description

In [28]: pd.Timestamp('2015-1-1 00:00', tz=pytz.FixedOffset(120))
Out[28]: Timestamp('2015-01-01 00:00:00+0200', tz='pytz.FixedOffset(120)')

It seems like I can create timestamps with a fixed offset, but I cannot convert from an existing timestamp to a fixed offset.

test.tz_convert('pytz.FixedOffset(-330)')
Traceback (most recent call last):
  File "/usr/lib/python3.8/code.py", line 90, in runcode
    exec(code, self.locals)
  File "<input>", line 1, in <module>
  File "pandas/_libs/tslibs/timestamps.pyx", line 2205, in pandas._libs.tslibs.timestamps.Timestamp.tz_convert
  File "pandas/_libs/tslibs/timezones.pyx", line 172, in pandas._libs.tslibs.timezones.maybe_get_tz
  File "/media/H/Python/Nevados/TRACE/_env/lib/python3.8/site-packages/pytz/__init__.py", line 188, in timezone
    raise UnknownTimeZoneError(zone)
pytz.exceptions.UnknownTimeZoneError: 'pytz.FixedOffset(-330)'

Alternative Solutions

I could put a feature request in with pytz instead.

Additional Context

Thank you!

Comment From: jbrockmendel

If you pass a pytz.FixedOffset object you should be OK. IIUC the trouble is in passing a string that pytz can't parse