Laying out a database schema for a calendar application

I have been struggling with the same problem, and I was actually toying with the "cache table" idea suggested above, but then I came across an alternative (suggested here) that doesn't seem to have been represented yet.

Build a table containing all events

EventID (primary key)
Description
StartDate
PeriodType - days, weeks, months, years
PeriodFreq - # of days, weeks, etc between events
EndDate
... other attributes that can be modified

Then add a table for exceptions to these events. This table uses a composite key, made up of the EventID that maps to the event table, and an instance ID to pick the particular event in the series.

EventID (key)
InstanceID (key)
InstanceDate - the modified date of the exception 
IsCancelled - a flag to skip this date when traversing the series
... other attributes that can be modified

It seems to keep the event table normalised, and avoids splitting up series to handle exceptions.

I recently created a calendar application and this was one of the many challenges that I faced.

I eventually came up with a semi hack-ish solution. I created an event_type column. In that column, I had either: daily, weekly, monthly, or yearly. I also had a start_date and an end_date columns. Everything else was handled in the actual backend code.

I never tried to split an event if a user edited only one event. It wasn't necessary in the situation. However, you could split an event by changing the end_date of the first, creating a new event with a new start_date and the end_date of the original, and finally, a new event for the one you just chose to edit. This process would end up creating 3 events.

Hack-ish, I know. I couldn't think of a clever way to handle this problem at the time.