make/data/tzdata/leapseconds

@@ -85,11 +85,17 @@
 Leap    2008    Dec     31      23:59:60        +       S
 Leap    2012    Jun     30      23:59:60        +       S
 Leap    2015    Jun     30      23:59:60        +       S
 Leap    2016    Dec     31      23:59:60        +       S
 
+# UTC timestamp when this leap second list expires.
+# Any additional leap seconds will come after this.
+# This Expires line is commented out for now,
+# so that pre-2020a zic implementations do not reject this file.
+#Expires 2020   Dec     28      00:00:00
+
 # POSIX timestamps for the data in this file:
 #updated 1467936000 (2016-07-08 00:00:00 UTC)
-#expires 1593302400 (2020-06-28 00:00:00 UTC)
+#expires 1609113600 (2020-12-28 00:00:00 UTC)
 
-#       Updated through IERS Bulletin C58
-#       File expires on:  28 June 2020
+#       Updated through IERS Bulletin C59
+#       File expires on:  28 December 2020