FW: Possible error in Tonga time zone

Paul Eggert eggert at twinsun.com
Tue Dec 7 23:01:22 UTC 1999

   From:	Jesper Nørgaard [SMTP:jnorgard at Prodigy.Net.mx]
   Sent:	Saturday, December 04, 1999 4:38 AM

   "Tonga now observes DST from the first Saturday in October until the Third
   Saturday in April.(Tonga will now be the first country to observe the year
   2000.) "

   In this case there is a discrepancy, since the third Sunday of
   April could fall on 15.th. of April, meaning that in that single
   case (which first happens 15.th.  of April 2001) Tonga will leave
   Daylight Saving at Sunday the 22.nd. of April 2001 according to the
   above rule, but at Sunday the 15.th. of April 2001 according to the
   web page informal rule.

The current rules are based on the following information from
Rives McDow (1999-10-06):

      Tonga started its Daylight Saving on Saturday morning October
      2nd at 0200am.  Daylight Saving ends on April 16 at 0300am which
      is Sunday morning.

>From this, I guessed that the informal statement ``until the Third
Saturday in April'' actually means ``until 0300 on the Sunday after
the third Saturday in April''.  This explains why the tz database
currently expects a DST change on 2001-04-22 instead of 2001-04-15.

If you have more authoritative information about Tonga, please let us know.

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