import datetime
now = datetime.datetime.now()
When time zone support is enabled (USE_TZ=True), Django uses
time-zone-aware datetime objects. If your code creates datetime objects, they
should be aware too. In this mode, the example above becomes:
from django.utils import timezone
now = timezone.now()
Warning
Dealing with aware datetime objects isn’t always intuitive. For instance,
the tzinfo argument of the standard datetime constructor doesn’t work
reliably for time zones with DST. Using UTC is generally safe; if you’re
using other time zones, you should review the zoneinfo
documentation carefully.
Python’s datetime.time objects also feature a tzinfo
attribute, and PostgreSQL has a matching time with time zone type.
However, as PostgreSQL’s docs put it, this type “exhibits properties which
lead to questionable usefulness”.
Django only supports naive time objects and will raise an exception if you
attempt to save an aware time object, as a timezone for a time with no
associated date does not make sense.
Interpretation of naive datetime objects
When USE_TZ is True, Django still accepts naive datetime
objects, in order to preserve backwards-compatibility. When the database layer
receives one, it attempts to make it aware by interpreting it in the
default time zone and raises a warning.
Unfortunately, during DST transitions, some datetimes don’t exist or are
ambiguous. That’s why you should always create aware datetime objects when time
zone support is enabled. (See the Using ZoneInfo section of the zoneinfo
docs for examples using the fold attribute to specify the
offset that should apply to a datetime during a DST transition.)
In practice, this is rarely an issue. Django gives you aware datetime objects
in the models and forms, and most often, new datetime objects are created from
existing ones through timedelta arithmetic. The only
datetime that’s often created in application code is the current time, and
timezone.now() automatically does the
right thing.
Default time zone and current time zone
The default time zone is the time zone defined by the TIME_ZONE
setting.
The current time zone is the time zone that’s used for rendering.
You should set the current time zone to the end user’s actual time zone with
activate(). Otherwise, the default time zone is
used.
As explained in the documentation of TIME_ZONE, Django sets
environment variables so that its process runs in the default time zone.
This happens regardless of the value of USE_TZ and of the
current time zone.
When USE_TZ is True, this is useful to preserve
backwards-compatibility with applications that still rely on local time.
However, as explained above, this isn’t
entirely reliable, and you should always work with aware datetimes in UTC
in your own code. For instance, use fromtimestamp()
and set the tz parameter to utc.
Selecting the current time zone
The current time zone is the equivalent of the current locale for translations. However, there’s no equivalent of the
Accept-Language HTTP header that Django could use to determine the user’s
time zone automatically. Instead, Django provides time zone selection
functions. Use them to build the time zone
selection logic that makes sense for you.
Most websites that care about time zones ask users in which time zone they live
and store this information in the user’s profile. For anonymous users, they use
the time zone of their primary audience or UTC.
zoneinfo.available_timezones() provides a set of available timezones that
you can use to build a map from likely locations to time zones.
Here’s an example that stores the current timezone in the session. (It skips
error handling entirely for the sake of simplicity.)
Add the following middleware to MIDDLEWARE:
import zoneinfo
from django.utils import timezone
class TimezoneMiddleware:
def __init__(self, get_response):
self.get_response = get_response
def __call__(self, request):
tzname = request.session.get("django_timezone")
if tzname:
timezone.activate(zoneinfo.ZoneInfo(tzname))
else:
timezone.deactivate()
return self.get_response(request)
Create a view that can set the current timezone:
from django.shortcuts import redirect, render
# Prepare a map of common locations to timezone choices you wish to offer.
common_timezones = {
"London": "Europe/London",
"Paris": "Europe/Paris",
"New York": "America/New_York",
def set_timezone(request):
if request.method == "POST":
request.session["django_timezone"] = request.POST["timezone"]
return redirect("/")
else:
return render(request, "template.html", {"timezones": common_timezones})
Include a form in template.html that will POST to this view:
{% load tz %}
{% get_current_timezone as TIME_ZONE %}
<form action="{% url 'set_timezone' %}" method="POST">
{% csrf_token %}
<label for="timezone">Time zone:</label>
<select name="timezone">
{% for city, tz in timezones %}
<option value="{{ tz }}"{% if tz == TIME_ZONE %} selected{% endif %}>{{ city }}</option>
{% endfor %}
</select>
<input type="submit" value="Set">
</form>
Time zone aware input in forms
When you enable time zone support, Django interprets datetimes entered in
forms in the current time zone and returns
aware datetime objects in cleaned_data.
Converted datetimes that don’t exist or are ambiguous because they fall in a
DST transition will be reported as invalid values.
Time zone aware output in templates
When you enable time zone support, Django converts aware datetime objects to
the current time zone when they’re rendered
in templates. This behaves very much like format localization.
Warning
Django doesn’t convert naive datetime objects, because they could be
ambiguous, and because your code should never produce naive datetimes when
time zone support is enabled. However, you can force conversion with the
template filters described below.
Conversion to local time isn’t always appropriate – you may be generating
output for computers rather than for humans. The following filters and tags,
provided by the tz template tag library, allow you to control the time zone
conversions.
Template tags
localtime
Enables or disables conversion of aware datetime objects to the current time
zone in the contained block.
This tag has exactly the same effects as the USE_TZ setting as far
as the template engine is concerned. It allows a more fine grained control of
conversion.
To activate or deactivate conversion for a template block, use:
{% load tz %}
{% localtime on %}
{{ value }}
{% endlocaltime %}
{% localtime off %}
{{ value }}
{% endlocaltime %}
The value of USE_TZ isn’t respected inside of a
{% localtime %} block.
timezone
Sets or unsets the current time zone in the contained block. When the current
time zone is unset, the default time zone applies.
{% load tz %}
{% timezone "Europe/Paris" %}
Paris time: {{ value }}
{% endtimezone %}
{% timezone None %}
Server time: {{ value }}
{% endtimezone %}
get_current_timezone
You can get the name of the current time zone using the
get_current_timezone tag:
{% get_current_timezone as TIME_ZONE %}
Alternatively, you can activate the
tz() context processor and
use the TIME_ZONE context variable.
Template filters
These filters accept both aware and naive datetimes. For conversion purposes,
they assume that naive datetimes are in the default time zone. They always
return aware datetimes.
localtime
Forces conversion of a single value to the current time zone.
For example:
{% load tz %}
{{ value|localtime }}
timezone
Forces conversion of a single value to an arbitrary timezone.
The argument must be an instance of a tzinfo subclass or a
time zone name.
For example:
{% load tz %}
{{ value|timezone:"Europe/Paris" }}
Migration guide
Here’s how to migrate a project that was started before Django supported time
zones.
Database
PostgreSQL
The PostgreSQL backend stores datetimes as timestamp with time zone. In
practice, this means it converts datetimes from the connection’s time zone to
UTC on storage, and from UTC to the connection’s time zone on retrieval.
As a consequence, if you’re using PostgreSQL, you can switch between USE_TZ
= False and USE_TZ = True freely. The database connection’s time zone
will be set to DATABASE-TIME_ZONE or UTC respectively, so that
Django obtains correct datetimes in all cases. You don’t need to perform any
data conversions.
Time zone settings
The time zone configured for the connection
in the DATABASES setting is distinct from the general
TIME_ZONE setting.
Other databases
Other backends store datetimes without time zone information. If you switch
from USE_TZ = False to USE_TZ = True, you must convert your data from
local time to UTC – which isn’t deterministic if your local time has DST.
Code
The first step is to add USE_TZ = True to your settings
file. At this point, things should mostly work. If you create naive datetime
objects in your code, Django makes them aware when necessary.
However, these conversions may fail around DST transitions, which means you
aren’t getting the full benefits of time zone support yet. Also, you’re likely
to run into a few problems because it’s impossible to compare a naive datetime
with an aware datetime. Since Django now gives you aware datetimes, you’ll get
exceptions wherever you compare a datetime that comes from a model or a form
with a naive datetime that you’ve created in your code.
So the second step is to refactor your code wherever you instantiate datetime
objects to make them aware. This can be done incrementally.
django.utils.timezone defines some handy helpers for compatibility
code: now(),
is_aware(),
is_naive(),
make_aware(), and
make_naive().
Finally, in order to help you locate code that needs upgrading, Django raises
a warning when you attempt to save a naive datetime to the database:
RuntimeWarning: DateTimeField ModelName.field_name received a naive
datetime (2012-01-01 00:00:00) while time zone support is active.
During development, you can turn such warnings into exceptions and get a
traceback by adding the following to your settings file:
import warnings
warnings.filterwarnings(
"error",
r"DateTimeField .* received a naive datetime",
RuntimeWarning,
r"django\.db\.models\.fields",
Fixtures
When serializing an aware datetime, the UTC offset is included, like this:
"2011-09-01T13:20:30+03:00"
While for a naive datetime, it isn’t:
"2011-09-01T13:20:30"
For models with DateTimeFields, this difference
makes it impossible to write a fixture that works both with and without time
zone support.
Fixtures generated with USE_TZ = False, or before Django 1.4, use the
“naive” format. If your project contains such fixtures, after you enable time
zone support, you’ll see RuntimeWarnings when you load them. To get
rid of the warnings, you must convert your fixtures to the “aware” format.
You can regenerate fixtures with loaddata then dumpdata.
Or, if they’re small enough, you can edit them to add the UTC offset that
matches your TIME_ZONE to each serialized datetime.
FAQ
Setup
I don’t need multiple time zones. Should I enable time zone support?
Yes. When time zone support is enabled, Django uses a more accurate model
of local time. This shields you from subtle and unreproducible bugs around
daylight saving time (DST) transitions.
When you enable time zone support, you’ll encounter some errors because
you’re using naive datetimes where Django expects aware datetimes. Such
errors show up when running tests. You’ll quickly learn how to avoid invalid
operations.
On the other hand, bugs caused by the lack of time zone support are much
harder to prevent, diagnose and fix. Anything that involves scheduled tasks
or datetime arithmetic is a candidate for subtle bugs that will bite you
only once or twice a year.
For these reasons, time zone support is enabled by default in new projects,
and you should keep it unless you have a very good reason not to.
I’ve enabled time zone support. Am I safe?
Maybe. You’re better protected from DST-related bugs, but you can still
shoot yourself in the foot by carelessly turning naive datetimes into aware
datetimes, and vice-versa.
If your application connects to other systems – for instance, if it queries
a web service – make sure datetimes are properly specified. To transmit
datetimes safely, their representation should include the UTC offset, or
their values should be in UTC (or both!).
Finally, our calendar system contains interesting edge cases. For example,
you can’t always subtract one year directly from a given date:
>>> import datetime
>>> def one_year_before(value): # Wrong example.
... return value.replace(year=value.year - 1)
>>> one_year_before(datetime.datetime(2012, 3, 1, 10, 0))
datetime.datetime(2011, 3, 1, 10, 0)
>>> one_year_before(datetime.datetime(2012, 2, 29, 10, 0))
Traceback (most recent call last):
ValueError: day is out of range for month
To implement such a function correctly, you must decide whether 2012-02-29
minus one year is 2011-02-28 or 2011-03-01, which depends on your business
requirements.
How do I interact with a database that stores datetimes in local time?
Set the TIME_ZONE option to the appropriate
time zone for this database in the DATABASES setting.
This is useful for connecting to a database that doesn’t support time zones
and that isn’t managed by Django when USE_TZ is True.
My application crashes with TypeError: can't compare offset-naive
and offset-aware datetimes – what’s wrong?
Let’s reproduce this error by comparing a naive and an aware datetime:
>>> from django.utils import timezone
>>> aware = timezone.now()
>>> naive = timezone.make_naive(aware)
>>> naive == aware
Traceback (most recent call last):
TypeError: can't compare offset-naive and offset-aware datetimes
If you encounter this error, most likely your code is comparing these two
things:
a datetime provided by Django – for instance, a value read from a form or
a model field. Since you enabled time zone support, it’s aware.
a datetime generated by your code, which is naive (or you wouldn’t be
reading this).
Generally, the correct solution is to change your code to use an aware
datetime instead.
If you’re writing a pluggable application that’s expected to work
independently of the value of USE_TZ, you may find
django.utils.timezone.now() useful. This function returns the current
date and time as a naive datetime when USE_TZ = False and as an aware
datetime when USE_TZ = True. You can add or subtract
datetime.timedelta as needed.
I see lots of RuntimeWarning: DateTimeField received a naive
datetime (YYYY-MM-DD HH:MM:SS) while time zone support is active
– is that bad?
When time zone support is enabled, the database layer expects to receive
only aware datetimes from your code. This warning occurs when it receives a
naive datetime. This indicates that you haven’t finished porting your code
for time zone support. Please refer to the migration guide for tips on this process.
In the meantime, for backwards compatibility, the datetime is considered to
be in the default time zone, which is generally what you expect.
now.date() is yesterday! (or tomorrow)
If you’ve always used naive datetimes, you probably believe that you can
convert a datetime to a date by calling its date()
method. You also consider that a date is a lot like a
datetime, except that it’s less accurate.
None of this is true in a time zone aware environment:
>>> import datetime
>>> import zoneinfo
>>> paris_tz = zoneinfo.ZoneInfo("Europe/Paris")
>>> new_york_tz = zoneinfo.ZoneInfo("America/New_York")
>>> paris = datetime.datetime(2012, 3, 3, 1, 30, tzinfo=paris_tz)
# This is the correct way to convert between time zones.
>>> new_york = paris.astimezone(new_york_tz)
>>> paris == new_york, paris.date() == new_york.date()
(True, False)
>>> paris - new_york, paris.date() - new_york.date()
(datetime.timedelta(0), datetime.timedelta(1))
>>> paris
datetime.datetime(2012, 3, 3, 1, 30, tzinfo=zoneinfo.ZoneInfo(key='Europe/Paris'))
>>> new_york
datetime.datetime(2012, 3, 2, 19, 30, tzinfo=zoneinfo.ZoneInfo(key='America/New_York'))
As this example shows, the same datetime has a different date, depending on
the time zone in which it is represented. But the real problem is more
fundamental.
A datetime represents a point in time. It’s absolute: it doesn’t depend
on anything. On the contrary, a date is a calendaring concept. It’s a
period of time whose bounds depend on the time zone in which the date is
considered. As you can see, these two concepts are fundamentally different,
and converting a datetime to a date isn’t a deterministic operation.
What does this mean in practice?
Generally, you should avoid converting a datetime to
date. For instance, you can use the date
template filter to only show the date part of a datetime. This filter will
convert the datetime into the current time zone before formatting it,
ensuring the results appear correctly.
If you really need to do the conversion yourself, you must ensure the
datetime is converted to the appropriate time zone first. Usually, this
will be the current timezone:
>>> from django.utils import timezone
>>> timezone.activate(zoneinfo.ZoneInfo("Asia/Singapore"))
# For this example, we set the time zone to Singapore, but here's how
# you would obtain the current time zone in the general case.
>>> current_tz = timezone.get_current_timezone()
>>> local = paris.astimezone(current_tz)
>>> local
datetime.datetime(2012, 3, 3, 8, 30, tzinfo=zoneinfo.ZoneInfo(key='Asia/Singapore'))
>>> local.date()
datetime.date(2012, 3, 3)
I get an error “Are time zone definitions for your database
installed?”
If you are using MySQL, see the Time zone definitions section
of the MySQL notes for instructions on loading time zone definitions.
I have a string "2012-02-21 10:28:45" and I know it’s in the
"Europe/Helsinki" time zone. How do I turn that into an aware
datetime?
Here you need to create the required ZoneInfo instance and attach it to
the naïve datetime:
>>> import zoneinfo
>>> from django.utils.dateparse import parse_datetime
>>> naive = parse_datetime("2012-02-21 10:28:45")
>>> naive.replace(tzinfo=zoneinfo.ZoneInfo("Europe/Helsinki"))
datetime.datetime(2012, 2, 21, 10, 28, 45, tzinfo=zoneinfo.ZoneInfo(key='Europe/Helsinki'))
How can I obtain the local time in the current time zone?
Well, the first question is, do you really need to?
You should only use local time when you’re interacting with humans, and the
template layer provides filters and tags
to convert datetimes to the time zone of your choice.
Furthermore, Python knows how to compare aware datetimes, taking into
account UTC offsets when necessary. It’s much easier (and possibly faster)
to write all your model and view code in UTC. So, in most circumstances,
the datetime in UTC returned by django.utils.timezone.now() will be
sufficient.
For the sake of completeness, though, if you really want the local time
in the current time zone, here’s how you can obtain it:
