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Editorial Team
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Asked: 2026-06-18T14:35:16+00:00

In my Django app I’ve got a Task model with some date and time

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In my Django app I’ve got a Task model with some date and time fields:

class Task(models.Model):

    date = models.DateField()
    start_time = models.TimeField(help_text='hh:mm')
    end_time = models.TimeField(help_text='hh:mm')
    # more stuff

I’ll send some Task instances to some Android clients that will be in a time zone (TZ1) different from my server time zone (TZ2).

The start_time and end_time fields must be set to the target time zone (TZ1), i.e. if I enter ’13:00′ in the start_time field in the Task admin, it should be ’13:00′ in TZ1.

How can I set the start_time and end_time values to be TZ1 times? If I leave the values entered in the default admin I guess the times will be set to the server time zone (TZ2), right?

Then what’s the best format to send these values (through JSON) to the Android clients to get the correct TZ2 time?

Now I’m using Python Datetime’s isoformat(), which gives something like

2013-02-11T13:17:23.811680

but it has no time zone data…

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1 Answer

  1. Editorial Team

    This is not the best way to handle timezones.

    The best way is to convert times to UTC as early as possible and convert them back as late as possible.

    In other words, if I enter the current time here as Feb 11, 21:03, it should never be stored like that. Instead it should be changed to UTC before anything else happens.

    That’s so, no matter what happens with it, it’s correct. If I send it to Inner Mongolia, it should stay as UTC right up until the point someone wants to look at it. Then and only then should it be converted (and for display only).

    Following that rule will save you a lot of grief in any software that has to work across multiple timezones. Trust me on that, we fixed a major Telco up after they’d implemented some hideous system that sent timezones across the wire, meaning that every point had to be able to convert to and from every timezone.

    Getting them into UTC as quickly as possible, and only getting them back on demand, saved bucketloads of time and money.

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