I think you are talking about on my iPhone, correct?
I so must be missing something....
I look in
Settings -> Mail, Contacts, Calendar
I scroll down and there isn't a "Sync" setting.
I look at all of the sections:
But don't see a "Sync" setting.
Am I looking right past it somewhere?
Connect your phone to iTunes on your computer and go to the Info tab of your iTunes sync settings. Under Sync Calendars make sure you haven't checked "Do not sync events older than...". If you have, uncheck this and click Apply at the bottom to sync your phone. Then see if your older events appear on your phone now.