Loaddata not dealing with timestamps and timezones properly

Question

I'm using django 1.4.1 with mysql and timezones enabled. I did a dump data to yaml, modified some fields to create some test data, and am trying to load it back in. however, Django keeps complaining about naive datetimes even though a tz is specified

specifically, my loaddata has:

fields: {created_date: !!timestamp '2012-09-15 22:17:44+00:00', ...

but loaddata gives the error:

RuntimeWarning: DateTimeField received a naive datetime (2012-09-15 22:17:44) while time zone support is active.

This doesn't make much sense to me, seeing as its:

1. a UTC timestamp
2. the same exact format Django exported using dumpdata

is there some way i can tell django this is a UTC date?

Answer 1

The problem stems from PyYAML. When loaddata hands off the datetime to PyYAML, it takes the aware datetime, adjusts the time to UTC, and then returns a naive datetime, which generates the warning.

There is a Django ticket, as well as a PyYAML ticket concerning the issue. Both go into far greater detail concerning the unexpected behavior above. Judging by the comments in the tickets, this issue seems unlikely to be resolved anytime soon.

Is you set TIME_ZONE = 'UTC' in settings.py of your project, you will load in the correct time, but you will still get warnings. Should your timezone be set to anything else, Django will treat the datetime as local, and adjust it to UTC, which is probably undesired.

The best way to avoid this is to use JSON as a serialization format.

Hope that helps.

Answer 2

From the docs...

When serializing an aware datetime, the UTC offset is included, like this:

"2011-09-01T13:20:30+03:00"

For a naive datetime, it obviously isn't:

"2011-09-01T13:20:30"

...so instead of...

created_date: !!timestamp '2012-09-15 22:17:44+00:00'

...either of...

created_date: '2012-09-15T22:17:44+00:00'

...or...

created_date: '2012-09-15T22:17:44Z'

...will work.