Only use the gmail address for google calendar sync
I had a similar problem, appointments showing up in the outlook deleted items folder and dated 1/1/1980. Took me some time to figure it out, but the solution is really simple. I have a secondary email address for my google account. I initially entered the secondary address in the outlook calendar sync, once I changed it to the gmail address, the problem was gone.
Just for the record, I am using a triple 2-way sync: home PC outlook to google, work PC outlook to google and android calendar on my smartphone to google. Only used the secondary address in one location. I also had problems like some appointments not showing up on the other side(s). Now that all syncs use the primary (= gmail) address, everything is working perfectly.