Convert UTC datetime string to local datetime

python

timezones

datetime

dateutil

byAlex Kataev·Feb 3, 2025

To convert a UTC datetime string to your local timezone, use the datetime and pytz packages. Parse the UTC string with datetime.strptime, attach the UTC timezone using replace(tzinfo=pytz.UTC), and finally convert to local time with astimezone(pytz.timezone('Your/Timezone')). Below is the crucial snippet:

from datetime import datetime
import pytz

utc_time_str = '2023-03-01T14:30:00'
local_dt = datetime.strptime(utc_time_str, '%Y-%m-%dT%H:%M:%S').replace(tzinfo=pytz.UTC).astimezone(pytz.timezone('Your/Timezone'))
print(local_dt)

Don't forget to substitute 'Your/Timezone' with your real local timezone, like so, 'Europe/Paris'. Let's walk through some key points.

Illuminating DST and standard timezone treatment

Dealing with timezones can be deceivingly complex due to elements like daylight saving time (DST). Let's avoid hardcoded offsets and let the libraries like dateutil or pytz handle DST.

# Who needs DST anyway, am I right?
from dateutil import tz

utc_time = datetime.strptime(utc_time_str, '%Y-%m-%dT%H:%M:%S').replace(tzinfo=tz.UTC)
local_time = utc_time.astimezone(tz.gettz('America/New_York'))  # Handles DST
print(local_time)

Consistent timezone storage

Storing the timezone information in canonical names like 'America/New_York' is key to achieving data consistency. Rely on the zoneinfo database for accurate timezone applications.

# No more "What time is it there?"
local_timezone = 'America/New_York'
local_dt = datetime.now(tz.gettz(local_timezone))
print(local_dt)

Quick local timezone detection

Automatically detecting the user's local timezone provides both accuracy and convenience. One quick way is using tzlocal.get_localzone().

# Just show the darn time!
from tzlocal import get_localzone

local_dt = datetime.utcnow().replace(tzinfo=tz.UTC).astimezone(get_localzone())
print(local_dt)

Custom timezone: because we can

Sometimes, because life isn't funny enough, you may need to define a custom timezone. For such joyful occasions, you can subclass datetime.tzinfo.

# Because we can
class CustomTimeZone(tzinfo):
    def utcoffset(self, dt):
        return timedelta(hours=3)  # Offset from UTC
    def dst(self, dt):
        return timedelta(0)  # No daylight saving time

Conversion magic: all the pitfalls and spells you need

Time conversion: It's not you, it's... Yes, it's you.

Time conversion is not always a walk in the park. Here are some hurdles:

Daylight saving time: Rules vary by location and they change. No one said it was going to be easy.
Leap seconds: Yes, they are a thing. Yes, they can affect your system.
Historical changes: Because changes in the past weren't complex enough, some regions decided to change their timezone definitions over time.

Programming like a pro

Some best practices for crafting top-notch time conversion code:

Use libraries like pytz and dateutil. They keep up-to-date with timezone rules so you don't have to.
Embrace the ISO 8601 formats when handling datetime strings.
Exceptions and edge cases, like invalid time zones, are not myths. Deal with them.