Want to clear Calendar of all events

Goal: Clear Calendar of all appointments/events

What I tried:
Went to Action/Purge: Set number of days to "1". Yet events/appointments older than one day are not erased. Nothing is changed. Even when I set the date on my ubuntu 3 years in the future all my events are still unerased.

I can delete each event one by one, but that's not time efficient.

I would like to clear all events because I there are events which are redundant (e.g.: 2 entries for "Christmas Day" on December 25). In the past, I used a Palm OS pda and had it sync to Evolution. But now I use a pocket pc. I'm still trying to fix the snyncing of my ubuntu (evolution) with my pocket pc.