If you want to see a really big Google Calendar, check out this calendar. Essentially, it is all the events from over 100 other calendars (all containing swing dancing events) merged into one, resulting in often more than 50 events every day, occasionally over 20 at the same time).

The data is approximately the same that can be seen on this map; in fact I’m trying to move the data keeping from a custom database (which has superior filtering capabilities such as synonyms in text search) to just having Google keep the data for me (meaning it will eventually not require me to have an own web server for this).

I’m doing some filtering such as removing events that don’t have parseable geo information (I’m adding GeoRSS:where elements, in fact), some text to html conversion of the entry contents and filtering out inappropriate events via some regular expressions (e.g. only including “Swing” not “Ballroom” events from a calendar)

There are still a couple of things to resolve. I’m not sure that recurrence exceptions are propagated properly to the combined calendar; the updates could work more incrementally, and I have to resolve some timezone issues due to the global nature of the calendar: I need to make sure the timezone information is preserved, since usually it makes more sense to give the events in local (to the event) time.

P.S. sorry, the code is too specialized and needs cleanup, I won’t share it yet.