I think that the best place to start would be our article titled Recovering iCloud or MobileMe data from iTunes backups for an iOS device found here: http://support.apple.com/kb/TS4108?viewlocale=en_US.
Take a look at step 2:
If you are an iCloud user, go to www.icloud.com and log in to iCloud Contacts or iCloud Calendar to see whether or not your missing data is there. If your missing data is available at iCloud.com, back up and recover from that data. Learn more about how to back up and recover your iCloud data. If any of the recovery methods listed there apply, use those.