Simon Perreault <simon.perreault@viagenie.ca> wrote on Tue, 2 Apr 2013 at 10:58:49 +0200 in <515A9DC9.8020009@viagenie.ca>:
I want to write a cron job or similar that activates one week prior to daylight saving time changes. (Or, more generically, one week prior to any time jumps, for any reason, DST or else.)
In casual interactive usage, I use the following, where 2014 is the subsequent calendar year: $ zdump -c 2014 -v US/Eastern | tail US/Eastern Sun Mar 11 06:59:59 2012 UTC = Sun Mar 11 01:59:59 2012 EST isdst=0 US/Eastern Sun Mar 11 07:00:00 2012 UTC = Sun Mar 11 03:00:00 2012 EDT isdst=1 US/Eastern Sun Nov 4 05:59:59 2012 UTC = Sun Nov 4 01:59:59 2012 EDT isdst=1 US/Eastern Sun Nov 4 06:00:00 2012 UTC = Sun Nov 4 01:00:00 2012 EST isdst=0 US/Eastern Sun Mar 10 06:59:59 2013 UTC = Sun Mar 10 01:59:59 2013 EST isdst=0 US/Eastern Sun Mar 10 07:00:00 2013 UTC = Sun Mar 10 03:00:00 2013 EDT isdst=1 US/Eastern Sun Nov 3 05:59:59 2013 UTC = Sun Nov 3 01:59:59 2013 EDT isdst=1 US/Eastern Sun Nov 3 06:00:00 2013 UTC = Sun Nov 3 01:00:00 2013 EST isdst=0 US/Eastern Mon Jan 18 03:14:07 2038 UTC = Sun Jan 17 22:14:07 2038 EST isdst=0 US/Eastern Tue Jan 19 03:14:07 2038 UTC = Mon Jan 18 22:14:07 2038 EST isdst=0 $ So that is one starting point. --jhawk@mit.edu John Hawkinson
Any pointers?
I have looked at the usual places: POSIX time functions, various date/time modules on CPAN, etc. Nothing seems to do that computation. Do I need to parse the tz database myself?