I discovered a number of strange entries in iCal on my iDevices which I didn't enter, and also were just on this device and neither my Mac nor the other device.
After a little search I found that my iPhone has a calendar for German holidays and the iPad a calendar for Swiss holidays. This is rather strange as I live in Austria and haven't visited these countries since the time I got these devices (>2 years). These calendars are in the section where also birthdays are and can not be edited or deleted. They also don't show up on iCal on the mac. I also checked the timezone on the devices - but this is set to Vienna - Austria.
So how would I fix them to Austrian holidays? - or at least delete so I won't be irritated by them.