Avoided mixing dates and datetimes in the examples.

Refs #16023.

docs/intro/overview.txt

@@ -31,7 +31,7 @@ the file ``mysite/news/models.py``::
             return self.full_name
 
     class Article(models.Model):
-        pub_date = models.DateTimeField()
+        pub_date = models.DateField()
         headline = models.CharField(max_length=200)
         content = models.TextField()
         reporter = models.ForeignKey(Reporter)
@@ -96,8 +96,8 @@ access your data. The API is created on the fly, no code generation necessary::
     DoesNotExist: Reporter matching query does not exist. Lookup parameters were {'id': 2}
 
     # Create an article.
-    >>> from datetime import datetime
-    >>> a = Article(pub_date=datetime.now(), headline='Django is cool',
+    >>> from datetime import date
+    >>> a = Article(pub_date=date.today(), headline='Django is cool',
     ...     content='Yeah.', reporter=r)
     >>> a.save()
 
@@ -140,7 +140,7 @@ as registering your model in the admin site::
     from django.db import models
 
     class Article(models.Model):
-        pub_date = models.DateTimeField()
+        pub_date = models.DateField()
         headline = models.CharField(max_length=200)
         content = models.TextField()
         reporter = models.ForeignKey(Reporter)