time-util: add note about on DST change

diff --git a/src/basic/time-util.c b/src/basic/time-util.c
index 7d44358cd84bef3ac45615c708f25be17ff3ad00..657e231b0d40870388eb27890183432ee84c7ea1 100644 (file)
--- a/src/basic/time-util.c
+++ b/src/basic/time-util.c
@@ -662,6 +662,9 @@ static int parse_timestamp_impl(
          *   +5min
          *   -5days
          *   @2147483647          (seconds since epoch)
+         *
+         * Note, on DST change, 00:00:00 may not exist and in that case the time part may be shifted.
+         * E.g. "Sun 2023-03-13 America/Havana" is parsed as "Sun 2023-03-13 01:00:00 CDT".
          */
 
         assert(t);