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filter dates to user profile's timezone

Author:
Scanner
Posted:
April 16, 2007
Language:
Python
Version:
.96
Tags:
filter timezone userprofile
Score:
4 (after 4 ratings)

I have users in many timezones and I let them set their preferred display timezone in their user profile as a string (validated aginst the pytz valid timezones).

This is a filter that takes a datetime as input and as an argument the user to figure out the timezone from.

It requires that there is a user profile model with a 'timezone' field. If a specific user does not have a user profile we fall back on the settings.TIME_ZONE. If the datetime is naieve then we again fallback on the settings.TIME_ZONE.

It requires the 'pytz' module: http://pytz.sourceforge.net/

Use: {{ post.created|user_tz:user|date:"D, M j, Y H:i" }}

The example is assuming a context in which the 'user' variable refers to a User object.

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import pytz
from django.conf import settings
from django.core.exceptions import ObjectDoesNotExist

@register.filter()
def user_tz(value, user):
    """Expects a datetime as the value. Expects a User object as the arg.
    Looks up the 'timezone' value in the user's profile, and converts
    the given datetime in to one in the user's timezone.

    NOTE: This assumes that you have the 'pytz' module
    (pytz.sourceforge.net) and that the user profile has a field
    called 'timezone' that is a character string and that the timezone
    thus specified is a valid timezone supported by pytz.
    """
    tz = settings.TIME_ZONE
    if isinstance(user, User):
        try:
            tz = user.get_profile().timezone
        except ObjectDoesNotExist:
            pass
    try:
        result = value.astimezone(pytz.timezone(tz))
    except ValueError:
        # Hm.. the datetime was stored 'naieve' ie: without timezone info.
        # we assume the timezone in 'settings' for all naieve objects.
        #
        result = value.replace(tzinfo=pytz.timezone(settings.TIME_ZONE)).astimezone(pytz.timezone(tz))
    return result

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Comments

derelm (on April 21, 2007):

i think a cleaner solution would be to pass the timezone as a parameter and not a user instance. the drawback would be more writing-work in your templates...

just my 2cents

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menendez (on June 5, 2008):

When using this filter I noticed that it was not converting time properly with naive dates between 'America/Chicago' and America/Sao_Paulo. It was adding an extra hour. To add the timezone to a naive date you should do something like this for line 28 (result = val..):

value = pytz.timezone(settings.TIME_ZONE).localize(value) result = value.astimezone(pytz.timezone(tz))

#

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