Fix erroneous and misleading example Doc to %y from %Y, use correct C99+ definition for C99 %D; update additional tests

Author: jyalim

Doc/library/datetime.rst

@@ -2534,7 +2534,7 @@ requires, and these work on all supported platforms.
 |  ``%d``   | Day of the month as a          | 01, 02, ..., 31        | \(9)  |
 |           | zero-padded decimal number.    |                        |       |
 +-----------+--------------------------------+------------------------+-------+
-|  ``%D``   | Equivalent to ``%m/%d/%y``.    | 11/28/2025             | \(9)  |
+|  ``%D``   | Equivalent to ``%m/%d/%y``.    | 11/28/25               | \(9)  |
 |           |                                |                        |       |
 +-----------+--------------------------------+------------------------+-------+
 |  ``%e``   | The day of the month as a      | ␣1, ␣2, ..., 31        |       |

Lib/_strptime.py

@@ -425,7 +425,7 @@ def __init__(self, locale_time=None):
         base.__setitem__('X', self.pattern(self.locale_time.LC_time))
         base.__setitem__('x', self.pattern(self.locale_time.LC_date))
         base.__setitem__('c', self.pattern(self.locale_time.LC_date_time))
-        base.__setitem__('D', self.pattern('%m/%d/%Y'))
+        base.__setitem__('D', self.pattern('%m/%d/%y'))
 
     def __seqToRE(self, to_convert, directive, altregex=None):
         """Convert a list to a regex string for matching a directive.

Lib/test/datetimetester.py

@@ -2201,10 +2201,10 @@ def test_strptime_F_format(self):
         )
 
     def test_strptime_D_format(self):
-        test_date = "11/28/2025"
+        test_date = "11/28/25"
         self.assertEqual(
             self.theclass.strptime(test_date, "%D"),
-            self.theclass.strptime(test_date, "%m/%d/%Y")
+            self.theclass.strptime(test_date, "%m/%d/%y")
         )
 
 

Lib/test/test_strptime.py

@@ -664,10 +664,10 @@ def test_strptime_T_format(self):
         )
 
     def test_strptime_D_format(self):
-        test_date = "11/28/2025"
+        test_date = "11/28/25"
         self.assertEqual(
             time.strptime(test_date, "%D"),
-            time.strptime(test_date, "%m/%d/%Y")
+            time.strptime(test_date, "%m/%d/%y")
         )
 
 class Strptime12AMPMTests(unittest.TestCase):