Thank you so much for your help, dianeoforegon! I'll answer your questions as best I can.
My style has been to sync via iTunes, using the Sync Services option in Entourage Preferences. I have always chosen a one-way sync from Entourage (i.e., overwriting iCal and Address Book) and done events and contacts in separate syncs. This seemed to prevent duplicates and was working successfully until I rashly upgraded to OS 10.7.5 [Lion, not Mountain Lion … for which my elderly MacBook (13-inch, early 2008) does not have the chops].
With one exception, iCal is now devoid of any events whatsoever, so even the decimated and duplicated events in Entourage are not showing up in iCal. The one exception in iCal is a daily Automator workflow, which I created in May 2011 to back up my main Entourage identity. As I remember, this was necessary because Time Machine's many incremental backups were corrupting my frequently changing Microsoft User Data, so I needed to exclude MUD from TM backups. The idea was that Automator's single daily backup would be stable enough to include in TM backups. I created the Automator workflow on the advice of Diane XXXX, an MVP in officeformac.com's Entourage forums. Could you and she be the same person?!
If the Automator workflow has been working properly, then I might be able to use this data to create an rge file as you suggest. However, when I click on the Database file in my Entourage Backup folder, where the Automator-created data is stored (overwriting the previous day’s backup), Entourage is launched and I'm faced with the decimated and duplicated calendar events. I think that means turning to the TM backups of this folder, each of which should have the then-current Entourage Backup folder. I'm still trying to figure out how to access the last pre-Lion backup; I started a search but canceled, because it seems to be an exceedingly slow process.
Alternatively, I figure the iTunes backup of my iPhone might prove a savior (I have done no syncing since the Lion upgrade; I'm carefully guarding the Calendar events on my iPhone) … although your comments make me wonder how I can access that backup and get it into Entourage. Maybe this is where iCloud comes into play.
I have never synced to iCloud calendars. If I remember correctly, there was a reason I didn't have access to iCloud at the time MobileMe was discontinued (June 30, 2012). I think it had to do with either the age of my MacBook or the age of my iPhone (original iPhone until late May 2012, when AT&T replaced it with an iPhone4, on which I am now running iOS 7.1.2).
Whatever the original problem was, I think it’s no longer relevant. I have just succeeded in signing into iCloud for the first time and discover that I do indeed have an existing account, but nothing has been set up. When I click on Mail, Contacts & Calendars in my MacBook's System Preferences, it says iCloud is inactive, shows my gmail accounts and offers to set up accounts to use with "Address Book, iCal, IChat, Mail and other apps." If I try the iCloud approach I'd appreciate any advice you have about setting up these accounts and making sure I migrate the right data.
Which of the two options I've come up with — (1) finding a TM backup of my main Entourage identity and somehow getting it into Entourage or (2) finding the iTunes backup of my iPhone and somehow getting that into Entourage — do you think most likely to succeed? Could you offer some pointers on how to start?
I would be grateful for any suggestions you have (maybe something completely different from the ideas I've come up with!).
Many, many thanks!