Merge branch 'doc-timestamp-f' into release-3.23

Merge-request: !7796

Help/command/string.rst

@@ -491,6 +491,8 @@ specifiers:
   The second of the current minute.  60 represents a leap second. (00-60)
 
 ``%f``
+  .. versionadded:: 3.23
+
   The microsecond of the current second (000000-999999).
 
 ``%U``