I think what is happening is the default "autoarchive" for calendars is 6 months, so once you are 6 months past your meeting it will be silently archived and removed from your active calendar. In outlook highlight calendar, then right click and go to properties, and look at the autoarchive settings. On mine it by default was set to 6 months and archives the stuff into a specific file. You can choose to turn off the autoarchiving on a folder by folder basis...you can have autoarchive delete rather than move entries, or you can specify where the archived entries are put! So you might want to just make a file "old meetings" and let autoarchive put stuff there.
But probably turning off autoarchive in the calendar folder would be your best bet.
An excerpt from my Outlook (Windows 2000 version 9.0.0.2711) help files follows. Hope this helps!
Paul
prhkgh@comcast.net
excerpt from Outlook help:
AutoArchive is a two-step process. First, you turn on AutoArchive. On the Tools menu, click Options, click the Other tab, and then click AutoArchive. Second, you set the AutoArchive properties for each folder that you want archived. At the folder level, you can determine which items are archived, and how often they are archived. You can automatically archive individual folders, groups of folders, or all Outlook folders. The process runs automatically whenever you start Outlook. The AutoArchive properties of each folder are checked by date, and old items are moved to your archive file. Items in the Deleted Items folder are deleted.
Several Outlook folders are set up with AutoArchive turned on. These folders and their default aging periods are Calendar (6 months), Tasks (6 months), Journal (6 months), Sent Items (2 months), and Deleted Items (2 months). Inbox, Notes, Contacts, and Drafts do not have AutoArchive activated automatically.