+
+# From Wikipedia <http://en.wikipedia.org/wiki/Time_zone> (2005-08-31):
+# Before 1920, all ships kept local apparent time on the high seas by setting
+# their clocks at night or at the morning sight so that, given the ship's
+# speed and direction, it would be 12 o'clock when the Sun crossed the ship's
+# meridian (12 o'clock = local apparent noon). During 1917, at the
+# Anglo-French Conference on Time-keeping at Sea, it was recommended that all
+# ships, both military and civilian, should adopt hourly standard time zones
+# on the high seas. Whenever a ship was within the territorial waters of any
+# nation it would use that nation's standard time. The captain was permitted
+# to change his ship's clocks at a time of his choice following his ship's
+# entry into another zone time--he often chose midnight. These zones were
+# adopted by all major fleets between 1920 and 1925 but not by many
+# independent merchant ships until World War II.
+
+# From Paul Eggert, using references suggested by Oscar van Vlijmen
+# (2005-03-20):
+#
+# The American Practical Navigator (2002)
+# <http://pollux.nss.nima.mil/pubs/pubs_j_apn_sections.html?rid=187>
+# talks only about the 180-degree meridian with respect to ships in
+# international waters; it ignores the international date line.