Need calendar for Galaxy S2 that syncs with google calendar.

Right now I use Outlook on my desktop which i synch with google calendar on my desktop which is synced to my Galaxy S2. The problem is that every time there is an OS update to the phone, the phone does not retain any info previous to the date of the update. The Outlook and google calendars on my desktop do synch correctly and have all my input going back a couple of years. How do I get to keep all of the previous calendar entries?
Thank you for your help.