Fix tests for IOS and add docs

Author: marat

Doc/library/datetime.rst

@@ -2762,11 +2762,17 @@ 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`` still requires a leading zero).
+   Use the ``%-`` flag to produce non-zero-padded output (e.g. ``%-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

@@ -1590,13 +1590,15 @@ def test_strftime(self):
         self.assertEqual(t.strftime('x'*1000), 'x'*1000) # SF bug #1556784
 
         # SF bug #137165
-        if platform.system() == 'Darwin':
+        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