"Mark Davis" <mark.davis@jtcsv.com> writes:
If two IDs have exactly the same behavior since the time when time zones were adopted, and have always been in the same country over that period, we only want one of them to be in the main list.
If two Olson zone names are aliased via a "Link" command in the Olson database, it could be that they are true aliases (e.g., Asia/Nicosia and Europe/Nicosia) or it could be that they happen to be same since 1970 and differed before then but we're not sure about the details (e.g., Europe/Oslo and Arctic/Longyearbyen) or it could be that they happen to have been the same since time zones were introduced but quite possibly will differ in the future (e.g., Antarctica/McMurdo and Antarctica/South_Pole). The database itself doesn't tell you which of these possibilities apply (though the comments give hints). However, one can safely conclude that if the Link command is in the "backward" or "etcetera" file then it is a true alias. I think that for your purposes it's probably safe to ignore all Link commands, except perhaps for those needed to establish the existence of an Olson zone name for a particular country. If by "country" one means ISO 3166 country code, these zone names would be: Arctic/Longyearbyen Europe/Bratislava Europe/Ljubljana Europe/San_Marino Europe/Sarajevo Europe/Skopje Europe/Vatican Europe/Zagreb