diff --git a/django/utils/dateformat.py b/django/utils/dateformat.py
index 9913c3f8c42..4e5f2bc8c0d 100644
--- a/django/utils/dateformat.py
+++ b/django/utils/dateformat.py
@@ -13,7 +13,7 @@ Usage:
 
 from django.utils.dates import MONTHS, MONTHS_AP, WEEKDAYS
 from django.utils.tzinfo import LocalTimezone
-from calendar import isleap
+from calendar import isleap, monthrange
 import re, time
 
 re_formatchars = re.compile(r'(?<!\\)([aABdDfFgGhHiIjlLmMnNOPrsStTUwWyYzZ])')
@@ -122,10 +122,6 @@ class DateFormat(TimeFormat):
         "Month, textual, long; e.g. 'January'"
         return MONTHS[self.data.month]
 
-    def I(self):
-        "'1' if Daylight Savings Time, '0' otherwise."
-        raise NotImplementedError
-
     def I(self):
         "'1' if Daylight Savings Time, '0' otherwise."
         if self.timezone.dst(self.data):
@@ -185,7 +181,7 @@ class DateFormat(TimeFormat):
 
     def t(self):
         "Number of days in the given month; i.e. '28' to '31'"
-        raise NotImplementedError
+        return '%02d' % monthrange(self.data.year, self.data.month)[1]
 
     def T(self):
         "Time zone of this machine; e.g. 'EST' or 'MDT'"
diff --git a/docs/templates.txt b/docs/templates.txt
index 955922811b8..53bd431e96e 100644
--- a/docs/templates.txt
+++ b/docs/templates.txt
@@ -552,7 +552,7 @@ Available format strings:
     s                 Seconds, 2 digits with leading zeros.     ``'00'`` to ``'59'``
     S                 English ordinal suffix for day of the     ``'st'``, ``'nd'``, ``'rd'`` or ``'th'``
                       month, 2 characters.
-    t                 Not implemented.
+    t                 Number of days in the given month.        ``28`` to ``31``
     T                 Time zone of this machine.                ``'EST'``, ``'MDT'``
     U                 Not implemented.
     w                 Day of the week, digits without           ``'0'`` (Sunday) to ``'6'`` (Saturday)