[tz] Rules for TZ+ database

[Guy Harris]

On Sep 5, 2013, at 1:02 PM, Patrice Scattolin <patrice.scattolin at oracle.com> wrote:

> Paul's scenario can and I am sure does occur especially in jurisdictions where the timezone changes are only known weeks in advanced from the date they take effect. That's a political problem not a software one.  I am sure that the people to whom this really matter (I am thinking the airline industries) probably track this carefully enough and are able to make the needed adjustment to their schedule. But you are right, in order for that to happen correctly both the time and the timezone has to be noted so that a correction can be applied properly.

As per my mail, the timezone, in the sense of the tzid for a zone, isn't necessarily going to be sufficient if the change involves the location of the event now being in a newly-created tzdb zone.  To handle that case automatically will involve an update to a set of machine-readable geographical-coordinates-to-tzid map and the geographical coordinates of the event.

(If the event ends up taking place at a location that straddles the tzdb zone boundary after the change, the correct answer might be to cancel the event and boycott that location in future events in order to punish the government for being blithering idiots; you *don't* put a time boundary right through a hotel if you're mentally competent. :-)  I'm not going to take seriously concerns about *that* edge case.)