From 2f6c0ce05e2f87f7c1867ea557160434bebe59f2 Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Wed, 17 Sep 2025 02:04:35 +0300
Subject: [PATCH 01/19] gh-137165: Add non-zero-padded Windows support for
 datetime.strftime

---
 Lib/_pydatetime.py                            | 15 +++++++
 Lib/test/datetimetester.py                    | 15 +++++++
 ...-09-16-15-36-18.gh-issue-137165.AclPcn.rst |  2 +
 Modules/_datetimemodule.c                     | 44 +++++++++++++++++++
 4 files changed, 76 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2025-09-16-15-36-18.gh-issue-137165.AclPcn.rst

diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
index b6d68f2372850a..50066df792fc7d 100644
--- a/Lib/_pydatetime.py
+++ b/Lib/_pydatetime.py
@@ -213,6 +213,11 @@ def _need_normalize_century():
             _normalize_century = True
     return _normalize_century
 
+def _make_dash_replacement(ch, timetuple):
+    fmt = '%' + ch
+    val = _time.strftime(fmt, timetuple)
+    return val.lstrip('0') or '0'
+
 # Correctly substitute for %z and %Z escapes in strftime formats.
 def _wrap_strftime(object, format, timetuple):
     # Don't call utcoffset() or tzname() unless actually needed.
@@ -284,6 +289,16 @@ def _wrap_strftime(object, format, timetuple):
                         push('{:04}'.format(year))
                         if ch == 'F':
                             push('-{:02}-{:02}'.format(*timetuple[1:3]))
+                elif ch == '-':
+                    if i < n:
+                        next_ch = format[i]
+                        i += 1
+                        if sys.platform.startswith('win') or sys.platform.startswith('android'):
+                            push(_make_dash_replacement(next_ch, timetuple))
+                        else:
+                            push('%-' + next_ch)
+                    else:
+                        push('%-')
                 else:
                     push('%')
                     push(ch)
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 2299d1fab2e73d..f509ad1cc9fafd 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -14,6 +14,7 @@
 import textwrap
 import unittest
 import warnings
+import platform
 
 from array import array
 
@@ -1588,6 +1589,15 @@ 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':
+            self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:05")
+        elif 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")
+        else:
+            self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:5")
+
         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
@@ -3890,6 +3900,11 @@ 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
+        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")
+
         # bpo-34482: Check that surrogates don't cause a crash.
         try:
             t.strftime('%H\ud800%M')
diff --git a/Misc/NEWS.d/next/Library/2025-09-16-15-36-18.gh-issue-137165.AclPcn.rst b/Misc/NEWS.d/next/Library/2025-09-16-15-36-18.gh-issue-137165.AclPcn.rst
new file mode 100644
index 00000000000000..bd4ab63eb19efe
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-09-16-15-36-18.gh-issue-137165.AclPcn.rst
@@ -0,0 +1,2 @@
+Add support for Windows non-zero-padded formatting directives in
+:func:`datetime.datetime.strftime` (e.g., ``"m:%-m d:%-d y:%-y"``).
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 12d316985fceb9..c8cc958ebf9cee 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1856,6 +1856,39 @@ make_freplacement(PyObject *object)
     return PyUnicode_FromString(freplacement);
 }
 
+#if defined(MS_WINDOWS) || defined(__ANDROID__)
+static PyObject *
+make_dash_replacement(PyObject *object, Py_UCS4 ch, PyObject *timetuple)
+{
+    PyObject *strftime = PyImport_ImportModuleAttrString("time", "strftime");
+    if (!strftime) {
+        return NULL;
+    }
+
+    char fmt[3] = {'%', (char)ch, 0};
+    PyObject *fmt_obj = PyUnicode_FromString(fmt);
+    if (!fmt_obj) {
+        Py_DECREF(strftime);
+        return NULL;
+    }
+
+    PyObject *res = PyObject_CallFunctionObjArgs(strftime, fmt_obj, timetuple, NULL);
+    Py_DECREF(fmt_obj);
+    Py_DECREF(strftime);
+    if (!res) {
+        return NULL;
+    }
+
+    PyObject *stripped = PyObject_CallMethod(res, "lstrip", "s", "0");
+    Py_DECREF(res);
+    if (!stripped) {
+        return NULL;
+    }
+
+    return stripped;
+}
+#endif
+
 /* I sure don't want to reproduce the strftime code from the time module,
  * so this imports the module and calls it.  All the hair is due to
  * giving special meanings to the %z, %:z, %Z and %f format codes via a
@@ -2002,6 +2035,17 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
             }
             continue;
         }
+        #if defined(MS_WINDOWS) || defined(__ANDROID__)
+        /* non-0-pad Windows support */
+        else if (ch == '-' && i < flen) {
+            Py_UCS4 next_ch = PyUnicode_READ_CHAR(format, i);
+            i++;
+            replacement = make_dash_replacement(object, next_ch, timetuple);
+            if (replacement == NULL) {
+                goto Error;
+            }
+        }
+        #endif
         else {
             /* percent followed by something else */
             continue;

From 8d169011f13a6d6b84c3131c361c1065d95fdfaf Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Thu, 18 Sep 2025 03:13:51 +0300
Subject: [PATCH 02/19] Refactor make_dash_replacement func and add negative
 test

---
 Lib/test/datetimetester.py                    |  5 +-
 ...-09-16-15-36-18.gh-issue-137165.AclPcn.rst |  2 -
 ...-09-18-03-02-39.gh-issue-137165.7tJ6DS.rst |  3 ++
 Modules/_datetimemodule.c                     | 46 +++++++++++--------
 4 files changed, 33 insertions(+), 23 deletions(-)
 delete mode 100644 Misc/NEWS.d/next/Library/2025-09-16-15-36-18.gh-issue-137165.AclPcn.rst
 create mode 100644 Misc/NEWS.d/next/Library/2025-09-18-03-02-39.gh-issue-137165.7tJ6DS.rst

diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index f509ad1cc9fafd..5031f2629e7e95 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -1592,10 +1592,9 @@ def test_strftime(self):
         # SF bug #137165
         if platform.system() == 'Darwin':
             self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:05")
-        elif 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")
         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.assertRaises(TypeError, t.strftime) # needs an arg
diff --git a/Misc/NEWS.d/next/Library/2025-09-16-15-36-18.gh-issue-137165.AclPcn.rst b/Misc/NEWS.d/next/Library/2025-09-16-15-36-18.gh-issue-137165.AclPcn.rst
deleted file mode 100644
index bd4ab63eb19efe..00000000000000
--- a/Misc/NEWS.d/next/Library/2025-09-16-15-36-18.gh-issue-137165.AclPcn.rst
+++ /dev/null
@@ -1,2 +0,0 @@
-Add support for Windows non-zero-padded formatting directives in
-:func:`datetime.datetime.strftime` (e.g., ``"m:%-m d:%-d y:%-y"``).
diff --git a/Misc/NEWS.d/next/Library/2025-09-18-03-02-39.gh-issue-137165.7tJ6DS.rst b/Misc/NEWS.d/next/Library/2025-09-18-03-02-39.gh-issue-137165.7tJ6DS.rst
new file mode 100644
index 00000000000000..eb8c562f28dfc8
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-09-18-03-02-39.gh-issue-137165.7tJ6DS.rst
@@ -0,0 +1,3 @@
+Standardized non-zero-padded date formatting in
+:func:`datetime.datetime.strftime` and :func:`datetime.date.strftime` across
+Windows and Unix. (e.g. ``"m:%-m d:%-d y:%-y"``).
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index c8cc958ebf9cee..38321a7cb5114b 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1860,32 +1860,42 @@ make_freplacement(PyObject *object)
 static PyObject *
 make_dash_replacement(PyObject *object, Py_UCS4 ch, PyObject *timetuple)
 {
-    PyObject *strftime = PyImport_ImportModuleAttrString("time", "strftime");
-    if (!strftime) {
-        return NULL;
+    PyObject *strftime = NULL;
+    PyObject *fmt_obj = NULL;
+    PyObject *res = NULL;
+    PyObject *stripped = NULL;
+
+    strftime = PyImport_ImportModuleAttrString("time", "strftime");
+    if (strftime == NULL) {
+        goto error;
     }
 
-    char fmt[3] = {'%', (char)ch, 0};
-    PyObject *fmt_obj = PyUnicode_FromString(fmt);
-    if (!fmt_obj) {
-        Py_DECREF(strftime);
-        return NULL;
+    fmt_obj = PyUnicode_FromFormat("%%%c", (char)ch);
+    if (fmt_obj == NULL) {
+        goto error;
     }
 
-    PyObject *res = PyObject_CallFunctionObjArgs(strftime, fmt_obj, timetuple, NULL);
-    Py_DECREF(fmt_obj);
-    Py_DECREF(strftime);
-    if (!res) {
-        return NULL;
+    res = PyObject_CallFunctionObjArgs(strftime, fmt_obj, timetuple, NULL);
+    if (res == NULL) {
+        goto error;
     }
 
-    PyObject *stripped = PyObject_CallMethod(res, "lstrip", "s", "0");
-    Py_DECREF(res);
-    if (!stripped) {
-        return NULL;
+    stripped = PyObject_CallMethod(res, "lstrip", "s", "0");
+    if (stripped == NULL) {
+        goto error;
     }
 
+    Py_DECREF(fmt_obj);
+    Py_DECREF(strftime);
+    Py_DECREF(res);
     return stripped;
+
+error:
+    Py_XDECREF(fmt_obj);
+    Py_XDECREF(strftime);
+    Py_XDECREF(res);
+    Py_XDECREF(stripped);
+    return NULL;
 }
 #endif
 
@@ -2036,7 +2046,7 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
             continue;
         }
         #if defined(MS_WINDOWS) || defined(__ANDROID__)
-        /* non-0-pad Windows support */
+        /* non-0-pad Windows and Android support */
         else if (ch == '-' && i < flen) {
             Py_UCS4 next_ch = PyUnicode_READ_CHAR(format, i);
             i++;

From 11e021843d37e47e3822bf091bbb88f513e022a7 Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Thu, 18 Sep 2025 16:42:13 +0300
Subject: [PATCH 03/19] Fix tests for IOS and add docs

---
 Doc/library/datetime.rst   | 8 +++++++-
 Lib/test/datetimetester.py | 4 +++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 7010f99c54da0a..433afa62af4168 100644
--- a/Doc/library/datetime.rst
+++ b/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
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 5031f2629e7e95..dad6bdcda26d9b 100644
--- a/Lib/test/datetimetester.py
+++ b/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

From eb5c88393ae921033ba845071267d3d48712edfd Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Thu, 18 Sep 2025 17:10:39 +0300
Subject: [PATCH 04/19] Update docs and news entry

---
 Doc/library/datetime.rst                                       | 2 +-
 .../Library/2025-09-18-03-02-39.gh-issue-137165.7tJ6DS.rst     | 3 ---
 .../Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst     | 3 +++
 3 files changed, 4 insertions(+), 4 deletions(-)
 delete mode 100644 Misc/NEWS.d/next/Library/2025-09-18-03-02-39.gh-issue-137165.7tJ6DS.rst
 create mode 100644 Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 433afa62af4168..4778e4622d92c6 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -2764,7 +2764,7 @@ Notes:
 (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).
+   ``%W``, ``%V`` and ``%y`` (except that on Apple platforms, ``%y`` always produces a leading zero).
    Use the ``%-`` flag to produce non-zero-padded output (e.g. ``%-d``).
 
 (10)
diff --git a/Misc/NEWS.d/next/Library/2025-09-18-03-02-39.gh-issue-137165.7tJ6DS.rst b/Misc/NEWS.d/next/Library/2025-09-18-03-02-39.gh-issue-137165.7tJ6DS.rst
deleted file mode 100644
index eb8c562f28dfc8..00000000000000
--- a/Misc/NEWS.d/next/Library/2025-09-18-03-02-39.gh-issue-137165.7tJ6DS.rst
+++ /dev/null
@@ -1,3 +0,0 @@
-Standardized non-zero-padded date formatting in
-:func:`datetime.datetime.strftime` and :func:`datetime.date.strftime` across
-Windows and Unix. (e.g. ``"m:%-m d:%-d y:%-y"``).
diff --git a/Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst b/Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst
new file mode 100644
index 00000000000000..3299a7f9f00412
--- /dev/null
+++ b/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 (e.g. ``"m:%-m d:%-d y:%-y"``).

From 224654c50605d842697e3368a9bdac9c0f047575 Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Thu, 18 Sep 2025 18:45:25 +0300
Subject: [PATCH 05/19] Fix 0 seconds/minutes strip and update docs

---
 Doc/library/datetime.rst   | 5 +++--
 Lib/test/datetimetester.py | 7 +++++--
 Modules/_datetimemodule.c  | 4 ++++
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 4778e4622d92c6..6ec23be6e12bab 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -2764,8 +2764,9 @@ Notes:
 (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 (e.g. ``%-d``).
+   ``%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
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index dad6bdcda26d9b..40120c36fa61e9 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -1589,7 +1589,7 @@ 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
+        # 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:
@@ -3901,11 +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')
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 38321a7cb5114b..25add396a22eef 100644
--- a/Modules/_datetimemodule.c
+++ b/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);

From 551f16e36774f597939a5d24cbd418f6c21d572e Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Thu, 18 Sep 2025 19:15:48 +0300
Subject: [PATCH 06/19] Update news entry

---
 .../next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst b/Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst
index 3299a7f9f00412..13ed317e60dfb8 100644
--- a/Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst
+++ b/Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst
@@ -1,3 +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 (e.g. ``"m:%-m d:%-d y:%-y"``).
+all platforms.

From ddc75ed650ca2282acceb1a5cb433f92aef555ed Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Fri, 19 Sep 2025 07:46:54 +0300
Subject: [PATCH 07/19] Unify strftime/ptime notes and refactor code

---
 Doc/library/datetime.rst | 13 ++++++-------
 Lib/_pydatetime.py       |  2 +-
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 6ec23be6e12bab..afb4bbc03cff17 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -2762,17 +2762,16 @@ 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.
 
+   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``. The ``%-`` flag (for example, ``%-d``) will produce
+   non-zero-padded output, except for ``%-y`` on Apple platforms, which is still
+   zero-padded.
+
 (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,
diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
index 50066df792fc7d..3475c2740931d6 100644
--- a/Lib/_pydatetime.py
+++ b/Lib/_pydatetime.py
@@ -293,7 +293,7 @@ def _wrap_strftime(object, format, timetuple):
                     if i < n:
                         next_ch = format[i]
                         i += 1
-                        if sys.platform.startswith('win') or sys.platform.startswith('android'):
+                        if sys.platform in ['win32', 'android']:
                             push(_make_dash_replacement(next_ch, timetuple))
                         else:
                             push('%-' + next_ch)

From a51dad631ac7caafd45e14e2d3b495d9c4233ca8 Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Fri, 19 Sep 2025 07:47:59 +0300
Subject: [PATCH 08/19] Update notes numbers

---
 Doc/library/datetime.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index afb4bbc03cff17..f047eb99f27417 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -2772,7 +2772,7 @@ Notes:
    non-zero-padded output, except for ``%-y`` on Apple platforms, which is still
    zero-padded.
 
-(11)
+(10)
    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

From 0e5ef8b6389aac0dae25db5da29cf41c70b49b5f Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Fri, 19 Sep 2025 13:46:26 +0300
Subject: [PATCH 09/19] Update datetime.rst

---
 Doc/library/datetime.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index f047eb99f27417..53736540e6431a 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -2766,8 +2766,8 @@ Notes:
    for  formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``,
    ``%W``, and ``%V``. Format ``%y`` does require a leading zero.
 
-   When used with the :meth:`~.datetime.strftime` method, the leading zero is optional
-   for formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``,
+   When used with the :meth:`~.datetime.strftime` method, leading zeroes are included
+   by default for formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``,
    ``%W``, ``%V`` and ``%y``. The ``%-`` flag (for example, ``%-d``) will produce
    non-zero-padded output, except for ``%-y`` on Apple platforms, which is still
    zero-padded.

From 375cf41de30a7dbc0befe73dc073989411535bdf Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Tue, 23 Sep 2025 18:49:25 +0300
Subject: [PATCH 10/19] Fix refleaks and tests for FreeBSD

---
 Doc/library/datetime.rst   | 4 ++--
 Lib/test/datetimetester.py | 2 +-
 Modules/_datetimemodule.c  | 1 +
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 53736540e6431a..7c169bac5b2e3b 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -2769,8 +2769,8 @@ Notes:
    When used with the :meth:`~.datetime.strftime` method, leading zeroes are included
    by default for formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``,
    ``%W``, ``%V`` and ``%y``. The ``%-`` flag (for example, ``%-d``) will produce
-   non-zero-padded output, except for ``%-y`` on Apple platforms, which is still
-   zero-padded.
+   non-zero-padded output, except for ``%-y`` on Apple platforms and FreeBSD,
+   which is still zero-padded.
 
 (10)
    When parsing a month and day using :meth:`~.datetime.strptime`, always
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 40120c36fa61e9..618bbce6b931d3 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -1590,7 +1590,7 @@ def test_strftime(self):
         self.assertEqual(t.strftime('x'*1000), 'x'*1000) # SF bug #1556784
 
         # See gh-137165
-        if platform.system() in ('Darwin', 'iOS'):
+        if platform.system() in ('Darwin', 'iOS', 'FreeBSD'):
             self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:05")
         else:
             if platform.system() == 'Windows':
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 25add396a22eef..df5c7083c32542 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1886,6 +1886,7 @@ make_dash_replacement(PyObject *object, Py_UCS4 ch, PyObject *timetuple)
     }
 
     if (PyUnicode_GET_LENGTH(stripped) == 0) {
+        Py_DECREF(stripped);
         stripped = PyUnicode_FromString("0");
     }
 

From 40d0e1c149dbff7ff31a2e78be4b7c4bf5317ff0 Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Wed, 24 Sep 2025 10:48:57 +0300
Subject: [PATCH 11/19] Fix refleaks

---
 Modules/_datetimemodule.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index df5c7083c32542..950591b3415603 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -2055,10 +2055,25 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
         else if (ch == '-' && i < flen) {
             Py_UCS4 next_ch = PyUnicode_READ_CHAR(format, i);
             i++;
-            replacement = make_dash_replacement(object, next_ch, timetuple);
-            if (replacement == NULL) {
+            
+            PyObject *tmp = make_dash_replacement(object, next_ch, timetuple);
+            if (tmp == NULL) {
+                Py_DECREF(tmp);
                 goto Error;
             }
+
+            if (PyUnicodeWriter_WriteSubstring(writer, format, start, end) < 0) {
+                Py_DECREF(tmp);
+                goto Error;
+            }
+            start = i;
+            if (PyUnicodeWriter_WriteStr(writer, tmp) < 0) {
+                Py_DECREF(tmp);
+                goto Error;
+            }
+
+            Py_DECREF(tmp);
+            continue;
         }
         #endif
         else {

From 2054356e5e96ff1882d25ec45316c0101f07cd97 Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Wed, 24 Sep 2025 11:03:29 +0300
Subject: [PATCH 12/19] Fix linting

---
 Modules/_datetimemodule.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 950591b3415603..22c3186c746073 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -2055,7 +2055,7 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
         else if (ch == '-' && i < flen) {
             Py_UCS4 next_ch = PyUnicode_READ_CHAR(format, i);
             i++;
-            
+
             PyObject *tmp = make_dash_replacement(object, next_ch, timetuple);
             if (tmp == NULL) {
                 Py_DECREF(tmp);

From 6ff5f4f385b895bacf6b01d7eb2c8b5aa4d6276f Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Thu, 25 Sep 2025 21:27:57 +0300
Subject: [PATCH 13/19] Refactor wrap_strftime func

---
 Modules/_datetimemodule.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 22c3186c746073..7f55bc50b78fcb 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1959,6 +1959,8 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
         i++;
         /* A % has been seen and ch is the character after it. */
         PyObject *replacement = NULL;
+        int need_decref_replacement = 0;
+
         if (ch == 'z') {
             /* %z -> +HHMM */
             if (zreplacement == NULL) {
@@ -2058,22 +2060,11 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
 
             PyObject *tmp = make_dash_replacement(object, next_ch, timetuple);
             if (tmp == NULL) {
-                Py_DECREF(tmp);
-                goto Error;
-            }
-
-            if (PyUnicodeWriter_WriteSubstring(writer, format, start, end) < 0) {
-                Py_DECREF(tmp);
-                goto Error;
-            }
-            start = i;
-            if (PyUnicodeWriter_WriteStr(writer, tmp) < 0) {
-                Py_DECREF(tmp);
                 goto Error;
             }
 
-            Py_DECREF(tmp);
-            continue;
+            replacement = tmp;
+            need_decref_replacement = 1;
         }
         #endif
         else {
@@ -2083,12 +2074,21 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
         assert(replacement != NULL);
         assert(PyUnicode_Check(replacement));
         if (PyUnicodeWriter_WriteSubstring(writer, format, start, end) < 0) {
+            if (need_decref_replacement) {
+                Py_DECREF(replacement);
+            }
             goto Error;
         }
         start = i;
         if (PyUnicodeWriter_WriteStr(writer, replacement) < 0) {
+            if (need_decref_replacement) {
+                Py_DECREF(replacement);
+            }
             goto Error;
         }
+        if (need_decref_replacement) {
+            Py_DECREF(replacement);
+        }
     }  /* end while() */
 
     PyObject *newformat;

From d5f2014681d7d9d8eb2a692388ba9993d043e2a3 Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Fri, 26 Sep 2025 16:05:20 +0300
Subject: [PATCH 14/19] Make replacement less complex

---
 Modules/_datetimemodule.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 7f55bc50b78fcb..6d76bc10ed3de9 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1921,6 +1921,7 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
     PyObject *colonzreplacement = NULL; /* py string, replacement for %:z */
     PyObject *Zreplacement = NULL;      /* py string, replacement for %Z */
     PyObject *freplacement = NULL;      /* py string, replacement for %f */
+    PyObject *dash_replacement = NULL;  /* py string, replacement for %- */
 
     assert(object && format && timetuple);
     assert(PyUnicode_Check(format));
@@ -2058,13 +2059,12 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
             Py_UCS4 next_ch = PyUnicode_READ_CHAR(format, i);
             i++;
 
-            PyObject *tmp = make_dash_replacement(object, next_ch, timetuple);
-            if (tmp == NULL) {
+            Py_XDECREF(dash_replacement);
+            dash_replacement = make_dash_replacement(object, next_ch, timetuple);
+            if (dash_replacement == NULL) {
                 goto Error;
             }
-
-            replacement = tmp;
-            need_decref_replacement = 1;
+            replacement = dash_replacement;
         }
         #endif
         else {
@@ -2074,21 +2074,12 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
         assert(replacement != NULL);
         assert(PyUnicode_Check(replacement));
         if (PyUnicodeWriter_WriteSubstring(writer, format, start, end) < 0) {
-            if (need_decref_replacement) {
-                Py_DECREF(replacement);
-            }
             goto Error;
         }
         start = i;
         if (PyUnicodeWriter_WriteStr(writer, replacement) < 0) {
-            if (need_decref_replacement) {
-                Py_DECREF(replacement);
-            }
             goto Error;
         }
-        if (need_decref_replacement) {
-            Py_DECREF(replacement);
-        }
     }  /* end while() */
 
     PyObject *newformat;
@@ -2115,6 +2106,7 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
     Py_XDECREF(colonzreplacement);
     Py_XDECREF(Zreplacement);
     Py_XDECREF(strftime);
+    Py_XDECREF(dash_replacement);
     return result;
 
  Error:

From 0d53cedac90a0ad7810540d8c8cd30a1353dc44b Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Fri, 26 Sep 2025 16:29:13 +0300
Subject: [PATCH 15/19] Remove useless variable

---
 Modules/_datetimemodule.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 6d76bc10ed3de9..98fa5eb62f156a 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1960,7 +1960,6 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
         i++;
         /* A % has been seen and ch is the character after it. */
         PyObject *replacement = NULL;
-        int need_decref_replacement = 0;
 
         if (ch == 'z') {
             /* %z -> +HHMM */

From 9212a5affcd796423a0b9fafd99a77e578c7840d Mon Sep 17 00:00:00 2001
From: marat <khagazheev@artlebedev.ru>
Date: Wed, 1 Oct 2025 23:32:15 +0300
Subject: [PATCH 16/19] Docs formatting and code style

---
 Doc/library/datetime.rst  | 9 +++++----
 Modules/_datetimemodule.c | 3 +--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 7c169bac5b2e3b..6c92a2505f07d3 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -2766,10 +2766,11 @@ Notes:
    for  formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``,
    ``%W``, and ``%V``. Format ``%y`` does require a leading zero.
 
-   When used with the :meth:`~.datetime.strftime` method, leading zeroes are included
-   by default for formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``,
-   ``%W``, ``%V`` and ``%y``. The ``%-`` flag (for example, ``%-d``) will produce
-   non-zero-padded output, except for ``%-y`` on Apple platforms and FreeBSD,
+   When used with the :meth:`~.datetime.strftime` method, leading zeroes
+   are included by default for formats ``%d``, ``%m``, ``%H``, ``%I``,
+   ``%M``, ``%S``, ``%j``, ``%U``, ``%W``, ``%V`` and ``%y``.
+   The ``%-`` flag (for example, ``%-d``) will produce non-zero-padded
+   output, except for ``%-y`` on Apple platforms and FreeBSD,
    which is still zero-padded.
 
 (10)
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 98fa5eb62f156a..7bab779a37d15a 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1960,7 +1960,6 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
         i++;
         /* A % has been seen and ch is the character after it. */
         PyObject *replacement = NULL;
-
         if (ch == 'z') {
             /* %z -> +HHMM */
             if (zreplacement == NULL) {
@@ -2104,8 +2103,8 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
     Py_XDECREF(zreplacement);
     Py_XDECREF(colonzreplacement);
     Py_XDECREF(Zreplacement);
-    Py_XDECREF(strftime);
     Py_XDECREF(dash_replacement);
+    Py_XDECREF(strftime);
     return result;
 
  Error:

From f74ad49b0b5cacf0f57ddee700f2803794c051d6 Mon Sep 17 00:00:00 2001
From: Lukasz Langa <ambv@meta.com>
Date: Wed, 21 Oct 2026 10:23:02 -0700
Subject: [PATCH 17/19] gh-137165: Only emulate `%-` for the documented numeric
 codes
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

On Windows and Android, every `%-X` was emulated by formatting `%X`
and stripping leading zeros.  That misbehaved for anything outside the
documented numeric codes: non-ASCII was narrowed to a byte (`%-Ť`
formatted the day, `%-é` raised OverflowError), `%-%` stuffed an
unescaped `%` into the format (`%-%d` gave the day), and `%-z`/`%-Z`
bypassed datetime's tzinfo handling.  Emulate only `%-d`, `%-m`,
`%-H`, `%-I`, `%-M`, `%-S`, `%-j`, `%-U`, `%-W`, `%-V` and `%-y`, and
leave everything else to the platform as before.

Gate the pure-Python branch the same way, so it no longer consumes
`%-%` as a unit on other platforms, which made `%-%f` differ from the
C implementation.  Use the cached time.strftime instead of importing it
on every call.

Co-authored-by: Muse Code (Meta Muse Spark)
---
 Lib/_pydatetime.py         | 16 ++++-----
 Lib/test/datetimetester.py | 23 ++++++++++++
 Modules/_datetimemodule.c  | 73 +++++++++++++++++---------------------
 3 files changed, 61 insertions(+), 51 deletions(-)

diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
index 8124f155a85610..26de468a500700 100644
--- a/Lib/_pydatetime.py
+++ b/Lib/_pydatetime.py
@@ -296,16 +296,12 @@ def _wrap_strftime(object, format, timetuple):
                         push('{:04}'.format(year))
                         if ch == 'F':
                             push('-{:02}-{:02}'.format(*timetuple[1:3]))
-                elif ch == '-':
-                    if i < n:
-                        next_ch = format[i]
-                        i += 1
-                        if sys.platform in ['win32', 'android']:
-                            push(_make_dash_replacement(next_ch, timetuple))
-                        else:
-                            push('%-' + next_ch)
-                    else:
-                        push('%-')
+                # The platform's strftime() lacks the %- flag (no zero
+                # padding), so emulate it for the documented numeric codes.
+                elif (ch == '-' and i < n and format[i] in 'dmHIMSjUWVy' and
+                        sys.platform in ['win32', 'android']):
+                    push(_make_dash_replacement(format[i], timetuple))
+                    i += 1
                 else:
                     push('%')
                     push(ch)
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 529f3dfb80ce40..e02f6884cfc706 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -1662,6 +1662,29 @@ def test_strftime_trailing_percent(self):
             _time.strftime("m:03 d:02 y:05 %", t.timetuple()),
         )
 
+    def test_strftime_dash_flag_passthrough(self):
+        # gh-137165: The %- flag is only emulated for the documented numeric
+        # codes.  Anything else after %- is left to the platform's strftime,
+        # so check that datetime's strftime acts the same as time.strftime.
+        t = self.theclass(2005, 3, 2)
+        tt = t.timetuple()
+
+        def outcome(func, *args):
+            try:
+                return func(*args)
+            except ValueError:
+                return ValueError
+
+        for fmt in ['%-', '%-#', '%-e', '%-Y', '%-z', '%-Z', '%-%d', '%-\0',
+                    '%-é', '%-Ť', '%-中']:  # low byte of 'Ť' is 'd'
+            with self.subTest(fmt=fmt):
+                self.assertEqual(outcome(t.strftime, fmt),
+                                 outcome(_time.strftime, fmt, tt))
+
+        # Format codes handled by datetime itself still work after %-.
+        self.assertEqual(outcome(t.strftime, '%-%f'),
+                         outcome(_time.strftime, '%-000000', tt))
+
     def test_format(self):
         dt = self.theclass(2007, 9, 10)
         self.assertEqual(dt.__format__(''), str(dt))
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 2d86ff39bc5f4d..9fb973b821857b 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1877,50 +1877,38 @@ make_freplacement(PyObject *object)
 }
 
 #if defined(MS_WINDOWS) || defined(__ANDROID__)
-static PyObject *
-make_dash_replacement(PyObject *object, Py_UCS4 ch, PyObject *timetuple)
+/* The documented numeric format codes for which the %- flag (no zero
+ * padding) is emulated.  Their output is digits only, so it needs no
+ * escaping before being stuffed into the format.
+ */
+static int
+is_dash_emulated(Py_UCS4 ch)
 {
-    PyObject *strftime = NULL;
-    PyObject *fmt_obj = NULL;
-    PyObject *res = NULL;
-    PyObject *stripped = NULL;
-
-    strftime = PyImport_ImportModuleAttrString("time", "strftime");
-    if (strftime == NULL) {
-        goto error;
-    }
-
-    fmt_obj = PyUnicode_FromFormat("%%%c", (char)ch);
-    if (fmt_obj == NULL) {
-        goto error;
+    switch (ch) {
+        case 'd': case 'm': case 'H': case 'I': case 'M': case 'S':
+        case 'j': case 'U': case 'W': case 'V': case 'y':
+            return 1;
+        default:
+            return 0;
     }
+}
 
-    res = PyObject_CallFunctionObjArgs(strftime, fmt_obj, timetuple, NULL);
+static PyObject *
+make_dash_replacement(PyObject *strftime, Py_UCS4 ch, PyObject *timetuple)
+{
+    assert(is_dash_emulated(ch));
+    char fmt[3] = {'%', (char)ch, '\0'};
+    PyObject *res = PyObject_CallFunction(strftime, "sO", fmt, timetuple);
     if (res == NULL) {
-        goto error;
-    }
-
-    stripped = PyObject_CallMethod(res, "lstrip", "s", "0");
-    if (stripped == NULL) {
-        goto error;
-    }
-
-    if (PyUnicode_GET_LENGTH(stripped) == 0) {
-        Py_DECREF(stripped);
-        stripped = PyUnicode_FromString("0");
+        return NULL;
     }
 
-    Py_DECREF(fmt_obj);
-    Py_DECREF(strftime);
+    PyObject *stripped = PyObject_CallMethod(res, "lstrip", "s", "0");
     Py_DECREF(res);
+    if (stripped != NULL && PyUnicode_GET_LENGTH(stripped) == 0) {
+        Py_SETREF(stripped, PyUnicode_FromString("0"));
+    }
     return stripped;
-
-error:
-    Py_XDECREF(fmt_obj);
-    Py_XDECREF(strftime);
-    Py_XDECREF(res);
-    Py_XDECREF(stripped);
-    return NULL;
 }
 #endif
 
@@ -2096,20 +2084,23 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
             }
             continue;
         }
-        #if defined(MS_WINDOWS) || defined(__ANDROID__)
-        /* non-0-pad Windows and Android support */
-        else if (ch == '-' && i < flen) {
+#if defined(MS_WINDOWS) || defined(__ANDROID__)
+        else if (ch == '-' && i < flen
+                 && is_dash_emulated(PyUnicode_READ_CHAR(format, i)))
+        {
+            /* %-d etc. -> no zero padding; the platform lacks this flag */
             Py_UCS4 next_ch = PyUnicode_READ_CHAR(format, i);
             i++;
 
             Py_XDECREF(dash_replacement);
-            dash_replacement = make_dash_replacement(object, next_ch, timetuple);
+            dash_replacement = make_dash_replacement(strftime, next_ch,
+                                                     timetuple);
             if (dash_replacement == NULL) {
                 goto Error;
             }
             replacement = dash_replacement;
         }
-        #endif
+#endif
         else {
             /* percent followed by something else */
             continue;

From ddf17eca39bb5865ce17b18fb0d437865187ffd6 Mon Sep 17 00:00:00 2001
From: Lukasz Langa <ambv@meta.com>
Date: Thu, 22 Oct 2026 17:13:33 -0700
Subject: [PATCH 18/19] gh-137165: Complete BSD support for non-zero-padded
 strftime

Emulate documented numeric dash flags on OpenBSD and account for NetBSD's
native zero padding of the short year. Cover 12-hour formatting at midnight,
noon and single-digit hours, document the version introducing support, and
include datetime.time.strftime in the NEWS entry.

Co-authored-by: Muse Code (Meta Muse Spark)
---
 Doc/library/datetime.rst                              |  5 ++++-
 Lib/_pydatetime.py                                    |  3 ++-
 Lib/test/datetimetester.py                            | 11 ++++++++++-
 .../2025-09-18-17-08-08.gh-issue-137165.sJase0.rst    |  4 ++--
 Modules/_datetimemodule.c                             |  4 ++--
 5 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index b793e5bd8e22f4..aac683c649a181 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -2923,9 +2923,12 @@ Notes:
    are included by default for formats ``%d``, ``%m``, ``%H``, ``%I``,
    ``%M``, ``%S``, ``%j``, ``%U``, ``%W``, ``%V`` and ``%y``.
    The ``%-`` flag (for example, ``%-d``) will produce non-zero-padded
-   output, except for ``%-y`` on Apple platforms and FreeBSD,
+   output, except for ``%-y`` on Apple platforms, FreeBSD and NetBSD,
    which is still zero-padded.
 
+   .. versionchanged:: 3.16
+      Support for the ``%-`` flag was added on Windows, Android and OpenBSD.
+
 (10)
    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,
diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
index 26de468a500700..c4c390f84410d5 100644
--- a/Lib/_pydatetime.py
+++ b/Lib/_pydatetime.py
@@ -299,7 +299,8 @@ def _wrap_strftime(object, format, timetuple):
                 # The platform's strftime() lacks the %- flag (no zero
                 # padding), so emulate it for the documented numeric codes.
                 elif (ch == '-' and i < n and format[i] in 'dmHIMSjUWVy' and
-                        sys.platform in ['win32', 'android']):
+                        (sys.platform in ('win32', 'android') or
+                         sys.platform.startswith('openbsd'))):
                     push(_make_dash_replacement(format[i], timetuple))
                     i += 1
                 else:
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index e02f6884cfc706..826b8753546303 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -1600,7 +1600,7 @@ def test_strftime(self):
         self.assertEqual(t.strftime('x'*1000), 'x'*1000) # SF bug #1556784
 
         # See gh-137165
-        if platform.system() in ('Darwin', 'iOS', 'FreeBSD'):
+        if platform.system() in ('Darwin', 'iOS', 'FreeBSD', 'NetBSD'):
             self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:05")
         else:
             if platform.system() == 'Windows':
@@ -4166,6 +4166,15 @@ def test_strftime(self):
         # gh-85432: The parameter was named "fmt" in the pure-Python impl.
         t.strftime(format="%f")
 
+    def test_strftime_dash_flag_12_hour(self):
+        # gh-137165: Midnight and noon are both 12 in the 12-hour clock.
+        for hour, expected in ((0, '12'), (1, '1'), (12, '12'),
+                               (13, '1'), (23, '11')):
+            with self.subTest(hour=hour):
+                t = self.theclass(hour)
+                self.assertEqual(t.strftime('%-I'), expected)
+                self.assertEqual(t.strftime('%I'), expected.zfill(2))
+
     def test_strftime_special(self):
         t = self.theclass(1, 2, 3, 4)
         s1 = t.strftime('%I%p%Z')
diff --git a/Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst b/Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst
index 13ed317e60dfb8..ff5cdace91f565 100644
--- a/Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst
+++ b/Misc/NEWS.d/next/Library/2025-09-18-17-08-08.gh-issue-137165.sJase0.rst
@@ -1,3 +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.
+:meth:`datetime.datetime.strftime`, :meth:`datetime.date.strftime` and
+:meth:`datetime.time.strftime` across all platforms.
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 9fb973b821857b..9a37f32d525208 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1876,7 +1876,7 @@ make_freplacement(PyObject *object)
     return PyUnicode_FromString(freplacement);
 }
 
-#if defined(MS_WINDOWS) || defined(__ANDROID__)
+#if defined(MS_WINDOWS) || defined(__ANDROID__) || defined(__OpenBSD__)
 /* The documented numeric format codes for which the %- flag (no zero
  * padding) is emulated.  Their output is digits only, so it needs no
  * escaping before being stuffed into the format.
@@ -2084,7 +2084,7 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
             }
             continue;
         }
-#if defined(MS_WINDOWS) || defined(__ANDROID__)
+#if defined(MS_WINDOWS) || defined(__ANDROID__) || defined(__OpenBSD__)
         else if (ch == '-' && i < flen
                  && is_dash_emulated(PyUnicode_READ_CHAR(format, i)))
         {

From 1022b42b324751d12a5017ee86207e35c27ebf53 Mon Sep 17 00:00:00 2001
From: Lukasz Langa <ambv@meta.com>
Date: Fri, 23 Oct 2026 23:20:47 +0200
Subject: [PATCH 19/19] gh-137165: Emulate %- flag on all platforms for
 consistency

Address review findings from gpshead:

- Emulate the documented numeric dash flags unconditionally in both
  C and pure-Python implementations, instead of gating by platform.
  This removes the hardcoded Windows/Android/OpenBSD list (and its
  duplication), fixes %-y on Apple, FreeBSD and NetBSD where the
  native libc ignores the flag, and makes the NEWS claim of
  "across all platforms" accurate.  No probe is needed since
  emulation via %X + lstrip('0') matches native output where the
  flag already works.

- Tests no longer branch by platform.system(), which misclassified
  iPadOS, tvOS, watchOS, visionOS and DragonFly.  Expectations are
  now unconditional, with an explanatory comment for %-y.  Windows
  %# checks use sys.platform, and the out-of-order `import platform`
  is gone.

- Docs: clarify the strftime paragraph in note (9) with an explicit
  "For formatting..." transition (kept under the same note number
  per mhsmith to avoid table clutter), and document that %- is
  emulated where the platform lacks it.

The %-%-d edge case is left as is: it shares the existing %-%f
quirk deliberately pinned by test_strftime_dash_flag_passthrough.

Co-authored-by: Muse Code (Meta Muse Spark)
---
 Doc/library/datetime.rst   | 15 ++++++++-------
 Lib/_pydatetime.py         | 10 +++++-----
 Lib/test/datetimetester.py | 20 ++++++++++----------
 Modules/_datetimemodule.c  | 12 +++++-------
 4 files changed, 28 insertions(+), 29 deletions(-)

diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index aac683c649a181..34c7cde9beb710 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -2919,15 +2919,16 @@ Notes:
    for  formats ``%d``, ``%m``, ``%H``, ``%I``, ``%M``, ``%S``, ``%j``, ``%U``,
    ``%W``, and ``%V``. Format ``%y`` does require a leading zero.
 
-   When used with the :meth:`~.datetime.strftime` method, leading zeroes
-   are included by default for formats ``%d``, ``%m``, ``%H``, ``%I``,
-   ``%M``, ``%S``, ``%j``, ``%U``, ``%W``, ``%V`` and ``%y``.
-   The ``%-`` flag (for example, ``%-d``) will produce non-zero-padded
-   output, except for ``%-y`` on Apple platforms, FreeBSD and NetBSD,
-   which is still zero-padded.
+   For formatting with the :meth:`~.datetime.strftime` method, leading
+   zeroes are included by default for formats ``%d``, ``%m``, ``%H``,
+   ``%I``, ``%M``, ``%S``, ``%j``, ``%U``, ``%W``, ``%V`` and ``%y``.
+   The ``%-`` flag (for example, ``%-d``) produces non-zero-padded
+   output on all platforms.
 
    .. versionchanged:: 3.16
-      Support for the ``%-`` flag was added on Windows, Android and OpenBSD.
+      The ``%-`` flag is now supported on all platforms.  It is emulated
+      where the platform C library lacks it, including on Windows, Android
+      and OpenBSD, and for ``%-y`` on Apple platforms, FreeBSD and NetBSD.
 
 (10)
    When parsing a month and day using :meth:`~.datetime.strptime`, always
diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
index c4c390f84410d5..9ea23a51c643b1 100644
--- a/Lib/_pydatetime.py
+++ b/Lib/_pydatetime.py
@@ -296,11 +296,11 @@ def _wrap_strftime(object, format, timetuple):
                         push('{:04}'.format(year))
                         if ch == 'F':
                             push('-{:02}-{:02}'.format(*timetuple[1:3]))
-                # The platform's strftime() lacks the %- flag (no zero
-                # padding), so emulate it for the documented numeric codes.
-                elif (ch == '-' and i < n and format[i] in 'dmHIMSjUWVy' and
-                        (sys.platform in ('win32', 'android') or
-                         sys.platform.startswith('openbsd'))):
+                # Emulate the %- flag (no zero padding) for the documented
+                # numeric codes, so behavior is consistent on all platforms.
+                # Some libcs lack the flag (Windows, Android, OpenBSD),
+                # others ignore it for %-y (Apple, FreeBSD, NetBSD).
+                elif ch == '-' and i < n and format[i] in 'dmHIMSjUWVy':
                     push(_make_dash_replacement(format[i], timetuple))
                     i += 1
                 else:
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 826b8753546303..92492fdbc95c31 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -15,7 +15,6 @@
 import textwrap
 import unittest
 import warnings
-import platform
 
 from array import array
 
@@ -1599,13 +1598,14 @@ def test_strftime(self):
         self.assertEqual(t.strftime(""), "") # SF bug #761337
         self.assertEqual(t.strftime('x'*1000), 'x'*1000) # SF bug #1556784
 
-        # See gh-137165
-        if platform.system() in ('Darwin', 'iOS', 'FreeBSD', 'NetBSD'):
-            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")
+        # gh-137165: The %- flag (no zero padding) is emulated for the
+        # documented numeric codes on all platforms, so expectations are
+        # the same everywhere.  In particular, %-y gives "5" here even
+        # though Apple, FreeBSD and NetBSD libcs still zero-pad it natively.
+        self.assertEqual(t.strftime("m:%-m d:%-d y:%-y"), "m:3 d:2 y:5")
+        if sys.platform == 'win32':
+            # Windows' native %# flag still passes through to the platform.
+            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.")
 
@@ -4149,9 +4149,9 @@ def test_strftime(self):
         # A naive object replaces %z, %:z and %Z with empty strings.
         self.assertEqual(t.strftime("'%z' '%:z' '%Z'"), "'' '' ''")
 
-        # See gh-137165
+        # gh-137165: %-H, %-M and %-S are emulated on all platforms.
         self.assertEqual(t.strftime('%-H %-M %-S %f'), "1 2 3 000004")
-        if platform.system() == 'Windows':
+        if sys.platform == 'win32':
             self.assertEqual(t.strftime('%#H %#M %#S %f'), "1 2 3 000004")
 
         t_zero = self.theclass(0, 0, 0, 4)
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 9a37f32d525208..3ee1592ae2f6e1 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1876,10 +1876,11 @@ make_freplacement(PyObject *object)
     return PyUnicode_FromString(freplacement);
 }
 
-#if defined(MS_WINDOWS) || defined(__ANDROID__) || defined(__OpenBSD__)
 /* The documented numeric format codes for which the %- flag (no zero
- * padding) is emulated.  Their output is digits only, so it needs no
- * escaping before being stuffed into the format.
+ * padding) is emulated on all platforms, so behavior is consistent.
+ * Some libcs lack the flag (Windows, Android, OpenBSD), others ignore
+ * it for %-y (Apple, FreeBSD, NetBSD).  Their output is digits only,
+ * so it needs no escaping before being stuffed into the format.
  */
 static int
 is_dash_emulated(Py_UCS4 ch)
@@ -1910,7 +1911,6 @@ make_dash_replacement(PyObject *strftime, Py_UCS4 ch, PyObject *timetuple)
     }
     return stripped;
 }
-#endif
 
 /* I sure don't want to reproduce the strftime code from the time module,
  * so this imports the module and calls it.  All the hair is due to
@@ -2084,11 +2084,10 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
             }
             continue;
         }
-#if defined(MS_WINDOWS) || defined(__ANDROID__) || defined(__OpenBSD__)
         else if (ch == '-' && i < flen
                  && is_dash_emulated(PyUnicode_READ_CHAR(format, i)))
         {
-            /* %-d etc. -> no zero padding; the platform lacks this flag */
+            /* %-d etc. -> no zero padding, emulated on all platforms */
             Py_UCS4 next_ch = PyUnicode_READ_CHAR(format, i);
             i++;
 
@@ -2100,7 +2099,6 @@ wrap_strftime(PyObject *object, PyObject *format, PyObject *timetuple,
             }
             replacement = dash_replacement;
         }
-#endif
         else {
             /* percent followed by something else */
             continue;