Merge branch 'bug/129'

* bug/129:
  doc, mention special zones (UTC, TAI, GPS)
  hygiene, update leap-seconds.list for upcoming release
  doc, add paragraph about default zone parameter, fixes #129

info/zone.texi

@@ -6,12 +6,18 @@ globally declare that date/time input is expressed in ZONE.
 Tools that output absolute date/times also allow @samp{--zone=ZONE} to
 globally declare that date/time output is to be converted into ZONE.
 
+When input or output zones are omitted dates and timestamps are treated
+as coming from the special (built-in) timezone UTC.
+
 Due to the complexity in setting up and maintaining timezone reference
 data, we decided to depart from our usual course and depend on the
 system's zoneinfo database.  As a consequence, @samp{ZONE} can point to
 anything in the system's zoneinfo directory which is assumed to be in
 IANA format.
 
+Zones @samp{UTC}, @samp{TAI}, and @samp{GPS} are treated specially.
+Their rules and offsets are built-in and never read from the disk.
+
 @heading Timezone maps
 
 Additionally, and true to our motto not to depend on system facilities,

lib/leap-seconds.list

@@ -62,7 +62,7 @@
 #		Terry Quinn, "The BIPM and the Accurate Measurement
 #		of Time," Proc. of the IEEE, Vol. 79, pp. 894-905,
 #		July, 1991. <http://dx.doi.org/10.1109/5.84965>
-#		reprinted in: 
+#		reprinted in:
 #		   Christine Hackman and Donald B Sullivan (eds.)
 #		   Time and Frequency Measurement
 #		   American Association of Physics Teachers (1996)
@@ -204,10 +204,10 @@
 #	current -- the update time stamp, the data and the name of the file
 #	will not change.
 #
-#	Updated through IERS Bulletin C58
-#	File expires on:  28 June 2020
+#	Updated through IERS Bulletin C61
+#	File expires on:  28 December 2021
 #
-#@	3802291200 
+#@	3849638400
 #
 2272060800	10	# 1 Jan 1972
 2287785600	11	# 1 Jul 1972
@@ -252,4 +252,4 @@
 #	the hash line is also ignored in the
 #	computation.
 #
-#h 	f28827d2 f263b6c3 ec0f19eb a3e0dbf0 97f3fa30
+#h 	2ab8253d d4380d28 75f01343 381504f8 8f8a4bfc