diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 4b351695a4..615b2b078b 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3086,6 +3086,10 @@ local0.* /var/log/postgresql
any time-zone-dependent %-escapes, the computation
is done in the zone specified
by .)
+ The supported %-escapes are similar to those
+ listed in the Open Group's strftime
+ specification.
Note that the system's strftime is not used
directly, so platform-specific (nonstandard) extensions do not work.