This might be a stupid question but I must have forgotten, because this never was an issue as far as I can remember.
My phone's calendar is set to displaying one calendar category (a subscription calendar "Swiss Holidays") and I cannot figure out how to switch to another category (I have "home" and "work" and a few more).
Since "Swiss Holidays" is a subscription calendar, I cannot add events to it. Plus it's suddenly not obvious how to add events anyway.
The phone is a 3GS running iOS 5.1.1, updated yesterday evening.