gh-137165: Standardized non-zero-padded date formatting for datetime.strftime

Doc/library/datetime.rst

@@ -2762,11 +2762,18 @@ Notes:
    interchangeable.
 
 (9)
+   When used with the :meth:`~.datetime.strftime` method, the leading zero is optional
+   for formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``,
+   ``%W``, ``%V`` and ``%y`` (except that on Apple platforms, ``%y`` always produces
+   a leading zero). Use the ``%-`` flag to produce non-zero-padded output
+   (for example, ``%-d``).
+
+(10)
    When used with the :meth:`~.datetime.strptime` method, the leading zero is optional
    for  formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``,
    ``%W``, and ``%V``. Format ``%y`` does require a leading zero.
 
-(10)
+(11)
    When parsing a month and day using :meth:`~.datetime.strptime`, always
    include a year in the format.  If the value you need to parse lacks a year,
    append an explicit dummy leap year.  Otherwise your code will raise an

Lib/test/datetimetester.py

@@ -1589,14 +1589,16 @@ def test_strftime(self):
         self.assertEqual(t.strftime(""), "") # SF bug #761337
         self.assertEqual(t.strftime('x'*1000), 'x'*1000) # SF bug #1556784
 
-        # SF bug #137165
-        if platform.system() == 'Darwin':
+        # See gh-137165
+        if platform.system() in ('Darwin', 'iOS'):
             self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:05")
         else:
             if platform.system() == 'Windows':
                 self.assertEqual(t.strftime("m:%#m d:%#d y:%#y"), "m:3 d:2 y:5")
             self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:5")
 
+        self.assertEqual(t.strftime("%-j. %-U. %-W. %-V."), "61. 9. 9. 9.")
+
         self.assertRaises(TypeError, t.strftime) # needs an arg
         self.assertRaises(TypeError, t.strftime, "one", "two") # too many args
         self.assertRaises(TypeError, t.strftime, 42) # arg wrong type
@@ -3899,11 +3901,14 @@ def test_strftime(self):
         # A naive object replaces %z, %:z and %Z with empty strings.
         self.assertEqual(t.strftime("'%z' '%:z' '%Z'"), "'' '' ''")
 
-        # SF bug #137165
+        # See gh-137165
         self.assertEqual(t.strftime('%-H %-M %-S %f'), "1 2 3 000004")
         if platform.system() == 'Windows':
             self.assertEqual(t.strftime('%#H %#M %#S %f'), "1 2 3 000004")
 
+        t_zero = self.theclass(0, 0, 0, 4)
+        self.assertEqual(t_zero.strftime('%-H %-M %-S %f'), "0 0 0 000004")
+
         # bpo-34482: Check that surrogates don't cause a crash.
         try:
             t.strftime('%H\ud800%M')

Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst

@@ -0,0 +1,3 @@
+Standardized non-zero-padded numeric formatting for dates and times in
+:func:`datetime.datetime.strftime` and :func:`datetime.date.strftime` across
+all platforms.

Modules/_datetimemodule.c

@@ -1885,6 +1885,10 @@ make_dash_replacement(PyObject *object, Py_UCS4 ch, PyObject *timetuple)
         goto error;
     }
 
+    if (PyUnicode_GET_LENGTH(stripped) == 0) {
+        stripped = PyUnicode_FromString("0");
+    }
+
     Py_DECREF(fmt_obj);
     Py_DECREF(strftime);
     Py_DECREF(res);