Fixed #26348 -- Added TruncTime and exposed it through the __time lookup.

Thanks Tim for the review.

docs/ref/models/database-functions.txt

@@ -686,6 +686,17 @@ that deal with time-parts can be used with ``TimeField``::
 truncate function. It's also registered as a transform on  ``DateTimeField`` as
 ``__date``.
 
+.. class:: TruncTime(expression, **extra)
+
+.. versionadded:: 1.11
+
+    .. attribute:: lookup_name = 'time'
+    .. attribute:: output_field = TimeField()
+
+``TruncTime`` casts ``expression`` to a time rather than using the built-in SQL
+truncate function. It's also registered as a transform on ``DateTimeField`` as
+``__time``.
+
 .. class:: TruncDay(expression, output_field=None, tzinfo=None, **extra)
 
     .. attribute:: kind = 'day'

docs/ref/models/querysets.txt

@@ -2674,6 +2674,27 @@ When :setting:`USE_TZ` is ``True``, datetime fields are converted to the
 current time zone before filtering. This requires :ref:`time zone definitions
 in the database <database-time-zone-definitions>`.
 
+.. fieldlookup:: time
+
+``time``
+~~~~~~~~
+
+.. versionadded:: 1.11
+
+For datetime fields, casts the value as time. Allows chaining additional field
+lookups. Takes a :class:`datetime.time` value.
+
+Example::
+
+    Entry.objects.filter(pub_date__time=datetime.time(14, 30))
+    Entry.objects.filter(pub_date__time__between=(datetime.time(8), datetime.time(17)))
+
+(No equivalent SQL code fragment is included for this lookup because
+implementation of the relevant query varies among different database engines.)
+
+When :setting:`USE_TZ` is ``True``, fields are converted to the current time
+zone before filtering.
+
 .. fieldlookup:: hour
 
 ``hour``