--- old/make/data/tzdata/leapseconds	2020-04-27 18:00:49.745354951 +0000
+++ new/make/data/tzdata/leapseconds	2020-04-27 18:00:49.365335775 +0000
@@ -87,9 +87,15 @@
 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