[nSLUG] Re: DST & tzdata

Mike mspencer at tallships.ca
Mon Mar 5 03:27:00 AST 2007

gnw> The files are tricky to read.  Look for the lines:
gnw> Rule  Canada  2007   max   -    Mar     Sun>=8  2:00    1:00    D
gnw> Rule  Canada  2007   max   -    Nov     Sun>=1  2:00    0       S
gnw> and note that America/Halifax is most recently (since 1974) set to
gnw> Canada.

Ah, yes.  I understand that, now that I've read that section of the
tzdata file more carefully.

> After you have installed the files,...

I'm alway overcautious about "installing" stuff (as root, obviously)
when I don't fully undestand what will happen.  So I unpacked the data
file in a user dir and ran "zic -d ." in various ways with confusing
results reported by zdump.

Annnd... finally figured out that zdump cannot be persuaded to dump a
particular file.  It can be *tricked* into doing so by manually
renaming the relevant file in the canonical location and copying into
its place the experimentally zic-compiled file.  Sigh...

gnw> $ zdump -v America/Halifax | grep 2007
gnw> America/Halifax  Sun Mar 11 05:59:59 2007 UTC = Sun Mar 11 01:59:59
gnw>       2007 AST isdst=0 gmtoff=-14400
gnw> America/Halifax  Sun Mar 11 06:00:00 2007 UTC = Sun Mar 11 03:00:00
gnw>      2007 ADT isdst=1 gmtoff=-10800
gnw> [snip]

Right.  Got that.  Good.  Thank you.

gnw> Do you keep your hardware clock (the one that runs from battery while
gnw> the system is off) on UTC?


So am I right in believing that I don't need all those other compiled
zoneinfo files for Ulan Bator or Tonga or even Toronto for ordinary
system operation?

- Mike

Michael Spencer                  Nova Scotia, Canada       .~. 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^


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