Answers for "how to change the timezone using datetime python"

convert timezone python

from datetime import datetime
from pytz import timezone, all_timezones
# must read else Bug:
# https://blog.ganssle.io/articles/2018/03/pytz-fastest-footgun.html

# aware dt-obj
dt_obj = datetime.strptime('2021-05-19T01:55:10+0000', '%Y-%m-%dT%H:%M:%S%z')
# double confirmaiton: aware dt-obj
dt_obj.tzinfo
# correct
dt_obj.astimezone(timezone('US/Pacific'))
# correct
dt_obj.replace(tzinfo=timezone('UTC')).astimezone(timezone('US/Pacific'))
# confirmation: desired tz
dt_obj.replace(tzinfo=timezone('UTC')).astimezone(timezone('US/Pacific')).tzinfo
# ~~~~~~~
# naive datetime object
datetime.utcnow()
# confirmation: naive dt-obj
print(datetime.utcnow().tzinfo)
# incorrect because started with naive datetime object
datetime.utcnow().astimezone(timezone('US/Pacific'))
# correct because add/replace tzinfo of initial dt-obj before conversion to desired tz
# SEE article link above. The following is probably correct only bc starting w/ utc.
datetime.utcnow().replace(tzinfo=timezone('UTC')).astimezone(timezone('US/Pacific'))
# confirmation: aware dt-obj
datetime.utcnow().replace(tzinfo=timezone('UTC')).astimezone(timezone('US/Pacific')).tzinfo

from dateutil import tz
dt=datetime(2018, 11, 1,20,0,0)

print(dt)
# 2018-11-01 20:00:00
print(dt.replace(tzinfo=tz.gettz('UTC')).astimezone(tz.gettz('US/Eastern')))
# 2018-11-01 16:00:00-04:00
print(datetime(2018, 11, 1,20,0,0,tzinfo=tz.gettz('UTC')).astimezone(tz.gettz('US/Eastern')))
# 2018-11-01 16:00:00-04:00
print(dt.replace(tzinfo=timezone('UTC')).astimezone(timezone('US/Eastern')))
# 2018-11-01 16:00:00-04:00
print(datetime(2018, 11, 1,20,0,0,tzinfo=timezone('UTC')).astimezone(timezone('US/Eastern')))
# 2018-11-01 16:00:00-04:00
print(timezone('UTC').localize(dt).astimezone(timezone('US/Eastern')))
# 2018-11-01 16:00:00-04:00

# ~~ VS ~~
dt=datetime(2018, 11, 1,16,0,0)
print(dt)
# 2018-11-01 16:00:00
print(dt.replace(tzinfo=tz.gettz('US/Eastern')).astimezone(tz.gettz('US/Pacific')))
# 2018-11-01 13:00:00-07:00
print(datetime(2018, 11, 1,16,0,0,tzinfo=tz.gettz('US/Eastern')).astimezone(tz.gettz('US/Pacific')))
# 2018-11-01 13:00:00-07:00
print(dt.replace(tzinfo=timezone('US/Eastern')).astimezone(timezone('US/Pacific'))) # Bug vector
# 2018-11-01 13:56:00-07:00 # incorrect!
print(datetime(2018, 11, 1,16,0,0,tzinfo=timezone('US/Eastern')).astimezone(timezone('US/Pacific'))) # Bug vector
# 2018-11-01 13:56:00-07:00 # incorrect!
print(timezone('US/Eastern').localize(dt).astimezone(timezone('US/Pacific')))
# 2018-11-01 13:00:00-07:00

# ~~~~~~~~~~~
# len(all_timezones) == 593
for zone in all_timezones:
    print(zone)

convert timezone python

import pytz
from dateutil import tz
from datetime import datetime, timedelta
# must read source link else Bug:

NYC_p = pytz.timezone('America/New_York')   # 1.53 µs
NYC_d = tz.gettz('America/New_York')        # 863 ns
# tz Awareness
dt_p = NYC_p.localize(datetime(2018, 11, 1))    # 35.4 µs
dt_d = datetime(2018, 11, 1, tzinfo=NYC_d)      # 1.38 µs

dt_p.utcoffset()        # 655 ns
dt_d.utcoffset()        # 13.9 µs

LA_p = pytz.timezone('America/Los_Angeles')
LA_d = tz.gettz('America/Los_Angeles')
# tz Conversion
NYC_p.localize(datetime(2018, 11, 1)).astimezone(LA_p)  # 44.8 µs
datetime(2018, 11, 1, tzinfo=NYC_d).astimzone(LA_d)     # 32.8 µs

# ~~~~~ Date Arithmetic
dt_winter = datetime(2018, 2, 14, 12, tzinfo=NYC_d)
dt_spring = dt_winter + timedelta(days=60)
print(dt_spring)
# 2018-04-15 12:00:00-04:00 # correct

dt_winter = NYC_p.localize(datetime(2018, 2, 14, 12)) # potential Bug vector1
dt_spring = dt_winter + timedelta(days=60)
print(dt_spring)
# 2018-04-15 12:00:00-05:00 # incorrect. subtle gotcha!
print(NYC_p.normalize(dt_spring)) # potential Bug vector2
# 2018-04-15 13:00:00-04:00 # correct