diff --git a/time/mktime.c b/time/mktime.c
index 8fe2f963ae..11b0d5353b 100644
--- a/time/mktime.c
+++ b/time/mktime.c
@@ -78,7 +78,7 @@ my_tzset (void)
        - Time zone names based on geography, without slashes, e.g.
          "Singapore".
        - Time zone names that contain explicit DST rules.  Syntax: see
-         <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03>
+         <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03>
      The Microsoft CRT understands only the first kind.  It produces incorrect
      results if the value of TZ is of the other kinds.
      But in a Cygwin environment, /etc/profile.d/tzset.sh sets TZ to a value