> 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".

Heh.  Run on local solar time and your job will be constantly running.

> 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.

Which is another point: do you _want_ it to get run if the machine was
down when the UTC offset shifted?  I can see arguments either way.

What if it's been down long enough that it's shifted back?  What if
multiple shifts have occurred but it's now not what it was last run?

The devil is in the details.

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