Fixed #17260 -- Added time zone aware aggregation and lookups.

Thanks Carl Meyer for the review.

Squashed commit of the following:

commit 4f290bdb60b7d8534abf4ca901bd0844612dcbda
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Wed Feb 13 21:21:30 2013 +0100

    Used '0:00' instead of 'UTC' which doesn't always exist in Oracle.

    Thanks Ian Kelly for the suggestion.

commit 01b6366f3ce67d57a58ca8f25e5be77911748638
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Wed Feb 13 13:38:43 2013 +0100

    Made tzname a parameter of datetime_extract/trunc_sql.

    This is required to work around a bug in Oracle.

commit 924a144ef8a80ba4daeeafbe9efaa826566e9d02
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Wed Feb 13 14:47:44 2013 +0100

    Added support for parameters in SELECT clauses.

commit b4351d2890cd1090d3ff2d203fe148937324c935
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Mon Feb 11 22:30:22 2013 +0100

    Documented backwards incompatibilities in the two previous commits.

commit 91ef84713c81bd455f559dacf790e586d08cacb9
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Mon Feb 11 09:42:31 2013 +0100

    Used QuerySet.datetimes for the admin's date_hierarchy.

commit 0d0de288a5210fa106cd4350961eb2006535cc5c
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Mon Feb 11 09:29:38 2013 +0100

    Used QuerySet.datetimes in date-based generic views.

commit 9c0859ff7c0b00734afe7fc15609d43d83215072
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Feb 10 21:43:25 2013 +0100

    Implemented QuerySet.datetimes on Oracle.

commit 68ab511a4ffbd2b811bf5da174d47e4dd90f28fc
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Feb 10 21:43:14 2013 +0100

    Implemented QuerySet.datetimes on MySQL.

commit 22d52681d347a8cdf568dc31ed032cbc61d049ef
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Feb 10 21:42:29 2013 +0100

    Implemented QuerySet.datetimes on SQLite.

commit f6800fd04c93722b45f9236976389e0b2fe436f5
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Feb 10 21:43:03 2013 +0100

    Implemented QuerySet.datetimes on PostgreSQL.

commit 0c829c23f4cf4d6804cadcc93032dd4c26b8c65e
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Feb 10 21:41:08 2013 +0100

    Added datetime-handling infrastructure in the ORM layers.

commit 104d82a7778cf3f0f5d03dfa53709c26df45daad
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Mon Feb 11 10:05:55 2013 +0100

    Updated null_queries tests to avoid clashing with the __second lookup.

commit c01bbb32358201b3ac8cb4291ef87b7612a2b8e6
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Feb 10 23:07:41 2013 +0100

    Updated tests of .dates().

    Replaced .dates() by .datetimes() for DateTimeFields.
    Replaced dates with datetimes in the expected output for DateFields.

commit 50fb7a52462fecf0127b38e7f3df322aeb287c43
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Feb 10 21:40:09 2013 +0100

    Updated and added tests for QuerySet.datetimes.

commit a8451a5004c437190e264667b1e6fb8acc3c1eeb
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Feb 10 22:34:46 2013 +0100

    Documented the new time lookups and updated the date lookups.

commit 29413eab2bd1d5e004598900c0dadc0521bbf4d3
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sun Feb 10 16:15:49 2013 +0100

    Documented QuerySet.datetimes and updated QuerySet.dates.

3 files changed, 58 insertions, 22 deletions

diff --git a/django/contrib/gis/db/models/sql/aggregates.py b/django/contrib/gis/db/models/sql/aggregates.py
index 9fcbb516d6..ae848c0894 100644
--- a/django/contrib/gis/db/models/sql/aggregates.py
+++ b/django/contrib/gis/db/models/sql/aggregates.py
@@ -22,13 +22,15 @@ class GeoAggregate(Aggregate):
             raise ValueError('Geospatial aggregates only allowed on geometry fields.')
 
     def as_sql(self, qn, connection):
-        "Return the aggregate, rendered as SQL."
+        "Return the aggregate, rendered as SQL with parameters."
 
         if connection.ops.oracle:
             self.extra['tolerance'] = self.tolerance
 
+        params = []
+
         if hasattr(self.col, 'as_sql'):
-            field_name = self.col.as_sql(qn, connection)
+            field_name, params = self.col.as_sql(qn, connection)
         elif isinstance(self.col, (list, tuple)):
             field_name = '.'.join([qn(c) for c in self.col])
         else:
@@ -36,13 +38,13 @@ class GeoAggregate(Aggregate):
 
         sql_template, sql_function = connection.ops.spatial_aggregate_sql(self)
 
-        params = {
+        substitutions = {
             'function': sql_function,
             'field': field_name
         }
-        params.update(self.extra)
+        substitutions.update(self.extra)
 
-        return sql_template % params
+        return sql_template % substitutions, params
 
 class Collect(GeoAggregate):
     pass
diff --git a/django/contrib/gis/db/models/sql/compiler.py b/django/contrib/gis/db/models/sql/compiler.py
index fc53d08ffd..b488f59362 100644
--- a/django/contrib/gis/db/models/sql/compiler.py
+++ b/django/contrib/gis/db/models/sql/compiler.py
@@ -1,14 +1,16 @@
+import datetime
 try:
     from itertools import zip_longest
 except ImportError:
     from itertools import izip_longest as zip_longest
 
-from django.utils.six.moves import zip
-
-from django.db.backends.util import truncate_name, typecast_timestamp
+from django.conf import settings
+from django.db.backends.util import truncate_name, typecast_date, typecast_timestamp
 from django.db.models.sql import compiler
 from django.db.models.sql.constants import MULTI
 from django.utils import six
+from django.utils.six.moves import zip
+from django.utils import timezone
 
 SQLCompiler = compiler.SQLCompiler
 
@@ -31,6 +33,7 @@ class GeoSQLCompiler(compiler.SQLCompiler):
         qn2 = self.connection.ops.quote_name
         result = ['(%s) AS %s' % (self.get_extra_select_format(alias) % col[0], qn2(alias))
                   for alias, col in six.iteritems(self.query.extra_select)]
+        params = []
         aliases = set(self.query.extra_select.keys())
         if with_aliases:
             col_aliases = aliases.copy()
@@ -61,7 +64,9 @@ class GeoSQLCompiler(compiler.SQLCompiler):
                         aliases.add(r)
                         col_aliases.add(col[1])
                 else:
-                    result.append(col.as_sql(qn, self.connection))
+                    col_sql, col_params = col.as_sql(qn, self.connection)
+                    result.append(col_sql)
+                    params.extend(col_params)
 
                     if hasattr(col, 'alias'):
                         aliases.add(col.alias)
@@ -74,15 +79,13 @@ class GeoSQLCompiler(compiler.SQLCompiler):
             aliases.update(new_aliases)
 
         max_name_length = self.connection.ops.max_name_length()
-        result.extend([
-                '%s%s' % (
-                    self.get_extra_select_format(alias) % aggregate.as_sql(qn, self.connection),
-                    alias is not None
-                        and ' AS %s' % qn(truncate_name(alias, max_name_length))
-                        or ''
-                    )
-                for alias, aggregate in self.query.aggregate_select.items()
-        ])
+        for alias, aggregate in self.query.aggregate_select.items():
+            agg_sql, agg_params = aggregate.as_sql(qn, self.connection)
+            if alias is None:
+                result.append(agg_sql)
+            else:
+                result.append('%s AS %s' % (agg_sql, qn(truncate_name(alias, max_name_length))))
+            params.extend(agg_params)
 
         # This loop customized for GeoQuery.
         for (table, col), field in self.query.related_select_cols:
@@ -98,7 +101,7 @@ class GeoSQLCompiler(compiler.SQLCompiler):
                 col_aliases.add(col)
 
         self._select_aliases = aliases
-        return result
+        return result, params
 
     def get_default_columns(self, with_aliases=False, col_aliases=None,
             start_alias=None, opts=None, as_pairs=False, from_parent=None):
@@ -280,5 +283,35 @@ class SQLDateCompiler(compiler.SQLDateCompiler, GeoSQLCompiler):
                 if self.connection.ops.oracle:
                     date = self.resolve_columns(row, fields)[offset]
                 elif needs_string_cast:
-                    date = typecast_timestamp(str(date))
+                    date = typecast_date(str(date))
+                if isinstance(date, datetime.datetime):
+                    date = date.date()
                 yield date
+
+class SQLDateTimeCompiler(compiler.SQLDateTimeCompiler, GeoSQLCompiler):
+    """
+    This is overridden for GeoDjango to properly cast date columns, since
+    `GeoQuery.resolve_columns` is used for spatial values.
+    See #14648, #16757.
+    """
+    def results_iter(self):
+        if self.connection.ops.oracle:
+            from django.db.models.fields import DateTimeField
+            fields = [DateTimeField()]
+        else:
+            needs_string_cast = self.connection.features.needs_datetime_string_cast
+
+        offset = len(self.query.extra_select)
+        for rows in self.execute_sql(MULTI):
+            for row in rows:
+                datetime = row[offset]
+                if self.connection.ops.oracle:
+                    datetime = self.resolve_columns(row, fields)[offset]
+                elif needs_string_cast:
+                    datetime = typecast_timestamp(str(datetime))
+                # Datetimes are artifically returned in UTC on databases that
+                # don't support time zone. Restore the zone used in the query.
+                if settings.USE_TZ:
+                    datetime = datetime.replace(tzinfo=None)
+                    datetime = timezone.make_aware(datetime, self.query.tzinfo)
+                yield datetime
diff --git a/django/contrib/gis/db/models/sql/where.py b/django/contrib/gis/db/models/sql/where.py
index ec078aebed..6ef34db0a3 100644
--- a/django/contrib/gis/db/models/sql/where.py
+++ b/django/contrib/gis/db/models/sql/where.py
@@ -44,8 +44,9 @@ class GeoWhereNode(WhereNode):
         lvalue, lookup_type, value_annot, params_or_value = child
         if isinstance(lvalue, GeoConstraint):
             data, params = lvalue.process(lookup_type, params_or_value, connection)
-            spatial_sql = connection.ops.spatial_lookup_sql(data, lookup_type, params_or_value, lvalue.field, qn)
-            return spatial_sql, params
+            spatial_sql, spatial_params = connection.ops.spatial_lookup_sql(
+                    data, lookup_type, params_or_value, lvalue.field, qn)
+            return spatial_sql, spatial_params + params
         else:
             return super(GeoWhereNode, self).make_atom(child, qn, connection)