Django issue #21523

21523.diff

diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index a4018dd..5acf520 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -1286,14 +1286,14 @@ class DateField(DateTimeCheckMixin, Field):
     def to_python(self, value):
         if value is None:
             return value
-        if isinstance(value, datetime.datetime):
+        if hasattr(value, 'tzinfo') and hasattr(value, 'date'):
             if settings.USE_TZ and timezone.is_aware(value):
                 # Convert aware datetimes to the default time zone
                 # before casting them to dates (#17742).
                 default_timezone = timezone.get_default_timezone()
                 value = timezone.make_naive(value, default_timezone)
             return value.date()
-        if isinstance(value, datetime.date):
+        if hasattr(value, 'year') and hasattr(value, 'month') and hasattr(value, 'day'):
             return value
 
         try:
@@ -1383,13 +1383,13 @@ class DateTimeField(DateField):
         if not timezone.is_naive(now):
             now = timezone.make_naive(now, timezone.utc)
         value = self.default
-        if isinstance(value, datetime.datetime):
+        if hasattr(value, 'tzinfo') and hasattr(value, 'date'):
             second_offset = datetime.timedelta(seconds=10)
             lower = now - second_offset
             upper = now + second_offset
             if timezone.is_aware(value):
                 value = timezone.make_naive(value, timezone.utc)
-        elif isinstance(value, datetime.date):
+        elif hasattr(value, 'year') and hasattr(value, 'month') and hasattr(value, 'day'):
             second_offset = datetime.timedelta(seconds=10)
             lower = now - second_offset
             lower = datetime.datetime(lower.year, lower.month, lower.day)
@@ -1420,9 +1420,9 @@ class DateTimeField(DateField):
     def to_python(self, value):
         if value is None:
             return value
-        if isinstance(value, datetime.datetime):
+        if hasattr(value, 'tzinfo') and hasattr(value, 'date'):
             return value
-        if isinstance(value, datetime.date):
+        if hasattr(value, 'year') and hasattr(value, 'month') and hasattr(value, 'day'):
             value = datetime.datetime(value.year, value.month, value.day)
             if settings.USE_TZ:
                 # For backwards compatibility, interpret naive datetimes in
@@ -2240,13 +2240,13 @@ class TimeField(DateTimeCheckMixin, Field):
         if not timezone.is_naive(now):
             now = timezone.make_naive(now, timezone.utc)
         value = self.default
-        if isinstance(value, datetime.datetime):
+        if hasattr(value, 'tzinfo') and hasattr(value, 'date'):
             second_offset = datetime.timedelta(seconds=10)
             lower = now - second_offset
             upper = now + second_offset
             if timezone.is_aware(value):
                 value = timezone.make_naive(value, timezone.utc)
-        elif isinstance(value, datetime.time):
+        elif hasattr(value, 'minute') and hasattr(value, 'second'):
             second_offset = datetime.timedelta(seconds=10)
             lower = now - second_offset
             upper = now + second_offset
@@ -2288,9 +2288,9 @@ class TimeField(DateTimeCheckMixin, Field):
     def to_python(self, value):
         if value is None:
             return None
-        if isinstance(value, datetime.time):
+        if hasattr(value, 'hour') and not hasattr(value, 'day'):
             return value
-        if isinstance(value, datetime.datetime):
+        if hasattr(value, 'time') and callable(value.time):
             # Not usually a good idea to pass in a datetime here (it loses
             # information), but this can be a side-effect of interacting with a
             # database backend (e.g. Oracle), so we'll be accommodating.