This is what I found on several threads, and it definitely worked for my EAS calendar:
1. Go to Date & Time and turn off Network time.
2. Change the Date to Jan 2 2009 (just change the year, not the month/day)
3. Launch calendar. Your entries should now be visible
4. Change the Date to the correct date - Jan 2 2010
5. Launch calendar again to verify that entries are still showing up
6. Switch network time back on
7. When "Waiting for Network" appear, switch to airplane mode
8. Turn airplane mode off, and network time should connect
9. Launch calendar again and it should be all good
Note that if you need to reset/turn off your Pre, you will need to do this all over again.