Can not extract/filter a Date(Time)Field when time zones are enabled ‹ troubleshooting ‹ Django antipatterns Fork me on GitHub

When using MySQL and we set the USE_TZ setting [Django-doc] to True, it can happen that certain (date)time-related queries no longer work.

What are the symptoms?

• If we .filter(…) [Django-doc] with an lookup of a DateField or DateTimeField, we retrieve an empty QuerySet, even though it should normally match some records. For example MyModel.objects.filter(created__date='1958-3-25') returns an empty QuerySet.
• If we .annotate(…) [Django-doc], then the annotated fields are NULL (None), for example if we use MyModel.objects.annotate(foo=ExtractMinute('created')), then the .foos of the retrieved objects are None.

What is a possible fix?

This often means that the MySQL database has not enough information about the time zones to do the extraction. Normally it stores data about time zones in the time_zone, time_zone_name, time_zone_transition and time_zone_transition_table of the mysql database, a database that is used to alter the settings of the database manager.

MySQL often comes with a script that can generate the SQL queries necessary based on the timezone files. Often these files are stored in the /usr/share/zoneinfo directory, so we can generate the queries with:

time_zone_transition /usr/share/zoneinfo

This of course does not changes the database itself. The queries need to be performed on the mysql database. We can do this manually or make use of a pipe and work with:

time_zone_transition /usr/share/zoneinfo | mysql -u root -p mysql

By entering the password of the root user (or another user that can alter the mysql database), we thus can update the tables to work with the (new) time zones.