Is it normal that when you do a data reset (with isync in the mac os control panel) your local ical calendars also get deleted?

I had to do a data reset sync and when the reset was done, all synced Zimbra calendars where there, but all my local calendars got deleted.

I'm using this version of isync: zimbra-isync-5.0.5_GA_2201.MACOSX_UB
Mac OS system version is Leopard 10.5.1

Thanks for any advice.