如何将datetime.time从UTC转换为不同的时区？

Question

I have variable which holds time which is of type datetime.time in UTC, I wanted it to convert to some other timezone.

we can convert timezones in datetime.datetime instance as shown in this SO link - How do I convert local time to UTC in Python? . I am not able to figure out how to convert timezones in datetime.time instances. I can't use astimezone because datetime.time doesn't have this method.

For example:

>>> t = d.datetime.now().time()
>>> t
datetime.time(12, 56, 44, 398402)
>>> 

I need 't' in UTC format.

Answer 1

I would create a temp datetime object, convert the tz, and extract the time again.

import datetime
def time_to_utc(t):
    dt = datetime.datetime.combine(datetime.date.today(), t)
    utc_dt = datetime_to_utc(dt)
    return utc_dt.time()

t = datetime.datetime.now().time()
utc_t = time_to_utc(t)

where, datetime_to_utc is any of the suggestions in the linked question .

Answer 2

There are four cases:

1. input datetime.time has tzinfo set (eg OP mentions UTC)
   1. output as non-naive time
   2. output as naive time ( tzinfo not set)
2. input datetime.time has tzinfo not set
   1. output as non-naive time
   2. output as naive time ( tzinfo not set)

The correct answer needs to make use of datetime.datetime.timetz() function because datetime.time cannot be built as a non-naive timestamp by calling localize() or astimezone() directly.

from datetime import datetime, time
import pytz

def timetz_to_tz(t, tz_out):
    return datetime.combine(datetime.today(), t).astimezone(tz_out).timetz()

def timetz_to_tz_naive(t, tz_out):
    return datetime.combine(datetime.today(), t).astimezone(tz_out).time()

def time_to_tz(t, tz_out):
    return tz_out.localize(datetime.combine(datetime.today(), t)).timetz()

def time_to_tz_naive(t, tz_in, tz_out):
    return tz_in.localize(datetime.combine(datetime.today(), t)).astimezone(tz_out).time()

Example based on OP requirement:

t = time(12, 56, 44, 398402)
time_to_tz(t, pytz.utc) # assigning tzinfo= directly would not work correctly with other timezones

datetime.time(12, 56, 44, 398402, tzinfo=<UTC>)

In case naive timestamp is wanted:

time_to_tz_naive(t, pytz.utc, pytz.timezone('Europe/Berlin'))

datetime.time(14, 56, 44, 398402)

The cases where the time() instance has already tzinfo set are easier because datetime.combine picks up the tzinfo from the passed parameter, so we just need to convert to tz_out .

Answer 3

Easy way to convert from/to UTC timezone using pytz :

import datetime, pytz

def time_to_utc(naive, timezone="Europe/Istanbul"):
    local = pytz.timezone(timezone)
    local_dt = local.localize(naive, is_dst=None)
    utc_dt = local_dt.astimezone(pytz.utc)
    return utc_dt

def utc_to_time(naive, timezone="Europe/Istanbul"):
    return naive.replace(tzinfo=pytz.utc).astimezone(pytz.timezone(timezone))

# type(naive) """DateTime"""
# type(timezone) """String"""

Answer 4

You need pytz . The use case you describe is illustrated in their primary examples.