You can synchronize your calendar history if you desire...
You will need the desktop manager software for this.
Connect the BB handheld and start the desktop manager software.
Go into the PIM sync configuration and switch the calendar from Wireless to the local mail application (Outlook, Notes, etc)
Confirm the change then from the main PIM configuration window, click advanced.
Click the radio button to change the option from "only future items" to "all entries"
Click OK then return to the main intellisync menu and synchronize the data.
All of your calendar entries, regardless of date will now be on your BlackBerry.
Reenable your wireless calendaring and you are on your way!