Get timezone for specific date

I have a list of dates formatted like so:

'2024-01-01`

I need to turn them into ISO datetimes like so:

`2024-01-01T00:00:00-08:00`

I thought this would be easy, I was wrong. I've seen many questions talk about this on SO, but they tend to over look the complexity of daylight savings time (DST).

What can't be used in a solution:

   datetime.now()

Using datetime.now() will give the current timezone, on the date it is today, and will not be relevant to the date in question.

I need to return the proper offest, when converting a specific date, based on what the offset would have been in local time at the date in question. Example:

'2024-01-01' # becomes
'2024-01-01T00:00:00-08:00'

'2024-06-06' # becomes
'2024-01-01T00:00:00-07:00'

I have a solution to brute force this by calculating daylight savings time start and finishes. But that's an ugly solution, there has to be some manipulation of the datetime api that works better.

Solution

from datetime import datetime
import pytz

def get_iso_datetime_with_timezone(date_str):
    date_obj = datetime.strptime(date_str, '%Y-%m-%d')

    aware_datetime_utc = pytz.utc.localize(date_obj)

    timezone = pytz.timezone('America/Los_Angeles')  # Example timezone, replace with your desired timezone

    aware_datetime_timezone = aware_datetime_utc.astimezone(timezone)

    iso_datetime_with_timezone = aware_datetime_timezone.strftime('%Y-%m-%dT%H:%M:%S%z')

    return iso_datetime_with_timezone

dates = ['2024-01-01', '2024-06-06']

for date_str in dates:
    iso_datetime_with_timezone = get_iso_datetime_with_timezone(date_str)
    print(f'{date_str} => {iso_datetime_with_timezone}')}

ensure you replace 'America/Los_Angeles' with the appropriate timezone for your use case you can find the list of supported timezones in the pytz documentation pytz handles historical timezone data so it will correctly account for DST changes on the specified date

NES ANSWER

from datetime import datetime
from zoneinfo import ZoneInfo

def get_iso_datetime_with_timezone(date_str, tz_name='America/Los_Angeles'):
    # Parse input date string to naive datetime object
    date_obj = datetime.strptime(date_str, '%Y-%m-%d')
    
    aware_datetime = date_obj.replace(tzinfo=ZoneInfo(tz_name))
    
    iso_datetime_with_timezone = aware_datetime.isoformat()
    
    return iso_datetime_with_timezone


dates = ['2024-01-01', '2024-06-06']

for date_str in dates:
    iso_datetime_with_timezone = get_iso_datetime_with_timezone(date_str)
    print(f'{date_str} => {iso_datetime_with_timezone}')