I recently had to move all of my Outlook 2007 stuff to 2002. First issue: Outlook 2007 does not give you any option to
export to an older data file format. The one used by 2002 has smaller capacity (read: different format) and no Unicode
support. There is a way around this: create a data file in the older Outlook 97-2002 Personal Folders file (.pst)
format and import items from the newer data file format to the older .pst file format. Then import that .pst into
Outlook 2002. You can read more about .pst data files in different versions of Outlook
here.
Second issue: Once you have imported all of your items into Outlook 2002, you may need to copy your calendar items to a different target calendar. You cannot just right click on the source calendar and copy all the items; if you paste onto the destination calendar, a subfolder will be created containing the source calendar. I know it’s stupid, but here’s an article to the rescue.