[tz] Fiji DST for 2012-2013 announced

[Ian Abbott]

On 2012-09-05 21:19, random832 at fastmail.us wrote:
> (oops, sent it directly instead of to the list at first)
>
> On Sun, Sep 2, 2012, at 00:12, lord.buddha at gmail.com wrote:
>> I now also wonder if the
>> presumption of a pattern might cause conflicts with other sources.
>> IATA / Microsoft etc.
>
> I think Microsoft's practice has generally been to have extrapolated
> rules, hope for the best, and publish a hotfix if it doesn't match. My
> (unpatched) Windows 7 machine extends the 2010 rule [Fourth Sunday
> October to Last Sunday March] on to infinity.

On my up-to-date Windows 7 system, the recurring rule for Fiji runs from 
the Fourth Sunday of October to the Fourth Sunday of January:

"TZI"=hex:30,fd,ff,ff,00,00,00,00,c4,ff,ff,ff,00,00,01,00,00,00,04,00,03,00,00,\
   00,00,00,00,00,00,00,0a,00,00,00,04,00,02,00,00,00,00,00,00,00

(see <http://msdn.microsoft.com/en-us/library/ms725481.aspx> for 
interpretation).

It currently has dynamic DST rules for years 2008 to 2013, but the 
information for the 2012-2013 DST period is currently incorrect.  They 
have DST beginning on the 4th Sunday of October 2012 (2012-10-28) and 
finishing on the 1st Sunday of March 2013 (2013-03-03):

"2012"=hex:30,fd,ff,ff,00,00,00,00,c4,ff,ff,ff,00,00,01,00,00,00,04,00,03,00,\
   00,00,00,00,00,00,00,00,0a,00,00,00,04,00,02,00,00,00,00,00,00,00
"2013"=hex:30,fd,ff,ff,00,00,00,00,c4,ff,ff,ff,00,00,03,00,00,00,01,00,03,00,\
   00,00,00,00,00,00,00,00,0a,00,00,00,04,00,02,00,00,00,00,00,00,00

Presumably they'll get round to fixing it on their next round of time 
zone updates.

> They have published at
> least two updates since then that I've been able to find that tweak the
> rules, and I haven't verified firsthand but have no particular reason to
> doubt they similarly extend the then-latest rules [Fourth Sunday January
> to First Sunday March, based on update description text] indefinitely,
> and expect to publish further hotfixes.

Microsoft's time zone information cannot encode penultimate Sundays, so 
if that's the rule, they'll have to use a "dynamic" DST rule each year, 
or change the way they store and interpret time zone information (which 
would have knock-on effects for applications that store and retrieve 
time zone information).

http://msdn.microsoft.com/en-us/library/ms725481.aspx

They don't store much historic information and only allow two 
transitions per year, so the temporary suspensions of DST by various 
also throw a spanner in the works, requiring hot-fixes to be applied at 
certain times of the year in those countries.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti at mev.co.uk>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-