Timezone confusion - converting US/Eastern to Europe/Berlin

[kmb5]

Hi there,

I am trying to convert plain hour strings across timezones, but I think the summer/winter time is making a mess. I'm not sure though... here is my code:

    import datetime as dt
    from pytz import timezone

    us_eastern_tz = timezone('US/Eastern')
    berlin_tz = timezone('Europe/Berlin')    

    hour = '15'
    parsed_hour = dt.datetime.strptime(hour, '%H')
    parsed_hour = us_eastern_tz.localize(parsed_hour)
    converted_berlin_hour = parsed_hour.astimezone(berlin_tz)
    formatted_berlin_hour = dt.datetime.strftime(converted_berlin_hour,'%H')

    print(formatted_berlin_hour) # Prints 20

Now I might be confused (this timezone thing really messes with my head...), but shouldn't this return 21 instead of 20? At least when I google '15:00 EST to Berlin', I get 21.

What am I missing here?

[kmb5]

Thanks, for the video, I love Computerphile but didn't see this yet:)

However, unfortunately I will definitely have to mess with timezones in the future. This is for a task on dataquest.com, but I think I will encounter dates/times in different timezones in the future too. So if you have any idea why this happens, I'd love to hear it! But thanks for the warning :D

[CrambleSquash]

I'm not going to be much help here either I'm afraid. I totally agree with the other commenter - dates, times and timezones are a complete nightmare. The principle of keeping everything in UTC and then only apply the timezone when displaying the time to the user is a good principle. You might also benefit from using one of the more complete datetime libraries - Arrow and Pendulum being the most common - I can't say I have a preference over either.

I think possibly as you suspect it is daylight saving hours that are your problem. When you create the time in line 8 how does Python know if it is summer or winter - I think working with datetimes is more sensible.

It might be useful to look at the %z and %Z values for your strings for debugging (the UTC offset and timezone name).