gh-154460: Do not use wcsftime() on OpenBSD (#154461)

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Stan Ulbrych <stan@python.org>

diff --git a/Misc/NEWS.d/next/Library/2026-07-22-13-00-00.gh-issue-154460.wCsFtM.rst b/Misc/NEWS.d/next/Library/2026-07-22-13-00-00.gh-issue-154460.wCsFtM.rst
new file mode 100644 (file)
index 0000000..b0a7058
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-07-22-13-00-00.gh-issue-154460.wCsFtM.rst
@@ -0,0 +1,2 @@
+Fix :func:`time.strftime` and :meth:`datetime.datetime.strftime` returning a
+wrong ISO 8601 week number (``%V``) on OpenBSD.

diff --git a/Modules/timemodule.c b/Modules/timemodule.c
index d90bf1f2ef90ed97020d04f183e9e8cb6c800404..70d7e1b3713687a079244eda56c11c53ebbae2c2 100644 (file)
--- a/Modules/timemodule.c
+++ b/Modules/timemodule.c
@@ -763,6 +763,13 @@ Other codes may be available on your platform.  See documentation for\n\
 the C library strftime function.\n"
 
 #ifdef HAVE_STRFTIME
+// gh-154460: OpenBSD's wcsftime() computes %V incorrectly: it returns 53
+// whenever the ISO 8601 week belongs to a different year than tm_year.
+// strftime() is not affected.
+#ifdef __OpenBSD__
+#  undef HAVE_WCSFTIME
+#endif
+
 #ifdef HAVE_WCSFTIME
 #define time_char wchar_t
 #define format_time wcsftime