As I am constantly factory resetting and flashing ROMs, I sometimes get annoyed as I lose all but the last 30 days of my Calendar history as this is how far the Google Calendar sync goes back. I have been playing about with this and found a solution. You can only go back ONE YEAR AT A TIME. 1. Ensure you are fully connected via wifi. 2. Go to Settings>Account and Sync. Turn off sync if it is on. 3. Go to Settings>Time + date. Turn off automatic date+time and Time Zone, and manually set your date to say 01/01/2012. 4. Go to Settings>Applications>All, and clear data for Calendar and Calendar Storage. 5. Reboot. 6. Keep the phone idle for a minute. 7. Ensure the system date is still the date to which you previously it set to. 8. Open up your Calendar app, Settings>Calendars and select all the Google calendars you require 9. Again, recheck the date on the phone. If it has changed to the current date, then set it back to the date you require. 10. If you are happy the date is "correct", go to Settings>Accounts and Sync. Manually synchronise your Calendar. 11. Open your Calendar app and you should see all your events for this year etc. 12. Go to Settings>Time + date. Manually set the date back to today's date, or turn automatic date+time and Time Zone back on if this is how you set it. 13. Go to Accounts and Sync and turn back on Sync if this is how you set it. NOTE: If you are rooted, I recommend you backup your Calendar and Calendar Storage before doing this just in case. Either use Titanium Backup, or go the whole hog and do a CWM Backup. NOTE2: For those of you constantly flashing ROMs who want all events for this year, it makes more sense on first boot to not set the phone to automatically obtain date+time, and manually set the date to 1st Jan in the setup wizard, and put it back to the correct date/automatic after google has synchronised all its stuff.