how to get UTC offset value from timezone? - django

Question

In my Django project, I have a form (forms.py) which implements pytz to get current timezone like this:
tz = timezone.get_current_timezone()
and I have passed this value to a form field as an initial value like this:
timezone = forms.CharField(label='Time Zone', initial=tznow)
which gives the field a default value of current Timezone, in my case, it happens to be Asia/Calcutta.
Now i want to find the UTC Offset value for the given Timezone, which in this case Asia/Calcutta is +5:30
I tried tzinfo() method as well, but i couldn't find the expected result. Can somebody guide me through this?

Answer 1

The UTC offset is given as a timedelta by the utcoffset method of any implementation of tzinfo such as pytz. For example:
import pytz
import datetime
tz = pytz.timezone('Asia/Calcutta')
dt = datetime.datetime.utcnow()
offset_seconds = tz.utcoffset(dt).total_seconds()
offset_hours = offset_seconds / 3600.0
print "{:+d}:{:02d}".format(int(offset_hours), int((offset_hours % 1) * 60))
# +5:30

Answer 2

A single timezone such as Asia/Calcutta may have different utc offsets at different dates. You can enumerate the utc offsets known so far using pytz's _tzinfos in this case:
>>> offsets = {off for off, dst, abbr in pytz.timezone('Asia/Calcutta')._tzinfos}
>>> for utc_offset in offsets:
... print(utc_offset)
...
5:30:00
6:30:00
5:53:00
To get the current utc offset for a given timezone:
#!/usr/bin/env python
from datetime import datetime
import pytz # $ pip install pytz
utc_offset = datetime.now(pytz.timezone('Asia/Calcutta')).utcoffset()
print(utc_offset)
# -> 5:30:00

Answer 3

In case you just want the normalized hour offset:
def curr_calcutta_offset():
tz_calcutta = pytz.timezone('Asia/Calcutta')
offset = tz_calcutta.utcoffset(datetime.utcnow())
offset_seconds = (offset.days * 86400) + offset.seconds
offset_hours = offset_seconds / 3600
return offset_hours
curr_calcutta_offset()
# 5.5