iCal, how can you do this to me?

After talking to Bruce, it seems that he has some of the same concerns for timezones that I do.

In a post, he pointed to something called VTIMEZONE. So, I went looking to see if perhaps there was another angle to this whole timezone storage mess.

VTIMEZONE is a data element attached to local times in iCal. It seems that when a recurring event is passed in iCal, it MUST have a VTIMEZONE component. So far so good. However, that VTIMEZONE record MUST specify information for DST! Bad iCal!

Of course, since this information is instantly incorrect, we end up with the problem we have had before. Even worse, because the information is fully specified in the message, developers are probably correct in assuming that they can't ignore the data and substitute their own information!

Personally, I feel this is a bug in iCal. I can see why it exists, to hand-wave around the timezone differences between Windows and OSX/Unix. At least they make a reference to the Olson (on which zoneinfo is based) database.

Developers, when implementing an iCal parser, use the VTIMEZONE value you receive as a way to determine the timezone, not as an actual descriptor. Based on the information in the VTIMEZONE component, find the timezone in your own TZ database and use that name when referring to the event. Never, ever, cache the definition.