>I think I like the idea of having a way to say
>
>   "please run this job whenever daylight savings starts or ends" 

change it to the more generic description

    "please run this job whenever local time shifts due to tz data"

and you've got something.  think "local sidereal time".

>in a crontab. IMHO cron is the right tool for this, already knows the local
>timezone and it should be easy to implement. Thoughts? Suggestions for the
>syntax?

sounds sorta like the @reboot pseudo-time, which doesn't get executed
because you rebooted the machine, but because you "rebooted" (or
restarted) cron itself.

keep in mind that you'll also have to keep local state in as atomic a
fashion as possible, since you can't guarantee that the machine will
be running when time shifts.

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