Django和时区

Question

Django 1.7, PostgreSQL.

I want to store datetime in UTC and display it in PST time zone.

My local time: 8:05 am

UTC time: 1:05 am

PST time: 6:05 pm

Django doc:

When support for time zones is enabled, Django stores date and time 
information in UTC in the database, uses time-zone-aware datetime objects 
internally, and translates them to the end user’s time zone in templates 
and forms.

setting.py

USE_TZ = True
TIME_ZONE = 'US/Pacific'

Model field

created_at = models.DateTimeField(auto_now_add=True)

I have created new model, and in django admin it display PST time (6:05 pm). It is OK. But if I do:

select created_at from my_table where id = 1;

It display my local time (8:05 am)! So, I'm not sure that this was stored in UTC time.

And one more thing.

Usual datetime field, I have set in admin this date: 2014-10-25 18:00:00

Id displayed in admin Oct. 25 , 2014, 6 pm

But select from DB show me:

2014-10- 26 08:00:00.0

So, I definitely do not understand what's going on. Where is my mistake?

Answer 1

Basically what happens is that time is stored in database using the timestamp, but displays the time using timezone specified in your database, which is unless manually changed is the timezone of the machine. But since you specify a different timezone in django, django will adjust the difference. So what you need to do is change the timezone in db to UTC (process differs depending on the engine)

The way I prefer to do it is leaving database timezone unchanged, specify 'UTC' in django settings, and then whenever displaying time to user, using some javascript convert it to local users time.

Edit

Didn't notice before that you are using PostgreSQL. I think you can just change timezone in postgresql.conf or change the TimeZone variable to UTC in database

Answer 2

I think Alexey Kuleshevich answers the first part of your question: When you do the manual select , PostgreSQL is displaying the timestamp in the timezone configured on the database. That doesn't affect Django, though, which is behaving according to the documentation.

As for the second part of your question: When you enter a datetime value in a form, Django interprets it in the current time zone , which by default is the same as your TIME_ZONE setting. So when you enter 6pm in the admin, Django interprets that as being 6pm PST, and stores it as 1am UTC (the next day). The database is then displaying that as 8am local time (the next day).