[Evolution] purge calendar

[gargarmel <gargarmel gmx net>]

hi! 

i just managed to sync my siemens S55 with evolution.
so lucky about that i did it twice. but second time was no sync but a
copy of all vCals from phone to evolution. there these exist twice.

so how may i delete all calendar entries from evo at once? 
deleting stuff in ~/evolution/local/Calendar doesn't work.

lucky about any hint. :)
regards, gargarmel.