The main problem is that django annotate datetime field to char will not work with certain datetime fields. For example, if you have a field called “created_at” and you try to annotate it with the CharField class, django will not allow you to save your data.
field I have a model with a datetime field and I want to annotate it to a charfield. I tried this: <code>MyModel.objects.values('date').annotate(date_char=CharField()) </code> but it gives me an error: <code>Cannot resolve keyword 'CharField' into field.</code> A: You can use <code>Func</code>: https://docs.djangoproject.com/en/dev/ref/models/expressions/#func-expressions and then use the <code>.format()</code> method on the resulting string to format it however you want (e.g., YYYY-MM-DD): https://docs.python.org/2/library/string.html#formatstrings . Something like this should work: <code>from django.db import models # for Func expression class from django import db # for connection alias, used in Func expression class # create connection alias, used in Func expression class # (this is only necessary if you are using multiple databases) # replace 'default' with your database name if using multiple databases my_conn = db._connections['default'] # create Func expression object that will convert date to string format YYYY-MM-DD my_func = models.Func(my_conn, function='TO_CHAR', template='%(function)s(%(expressions)s::DATE, 'YYYY-MM-DD')') # use my_func in query as follows: MyModelObjects = MyModelObjects .objects .values('date') .annotate(date_char=my_func) </code>
Datetime in Django
Django provides a convenient datetime type that can be used to represent dates and times.
To create a datetime object, use the datetime constructor:
>>> from django.utils.datetime import datetime >>> d = datetime(2015, 11, 25) >>> d 2015-11-25 00:00:00
Examples of datetime code
The following is a list of example datetime code in Django.
from django.utils.datetime import datetime from django.utils.translation import gettext_lazy as _ from django.core.urlresolvers import reverse from django.db import models class User(models.Model): first_name = models.CharField(max_length=30, blank=True, nullable=False) last_name = models.CharField(max_length=30, blank=True, nullable=False) email = models.EmailField() def __str__(self): return self._first_name + ‘ ‘ + self._last_name + ‘@’ + self._email