I'm looking at some legacy code that generates an .ics invitation. There are a ton of RDATE fields in the file, and they seem to repeat by year, starting in 1918. This is for a meeting in 2013, so it seems like all these RDATEs are not necessary and maybe something is wrong. Do you think so? Any suggestions on where to look?
Typically that many RDATE properties are found in VTIMEZONE components of an iCalendar file, and looking at those dates (1918, 1919, etc.) I would hazard a guess that these are timezone definitions in your files.
So the short answer is that they are most likely not all required, especially if your events are not using the specified timezones, however I would be careful when editing timezone definitions to make sure you aren't changing the rules for events that use it (i.e. you could safely remove RDATE:1918, etc. assuming you don't have any events occurring in 1918).