That is why I always back up my google data, everything from calendar to the docs and most importantly emails.
I spent a weekend defining a process checking it making sure it works, tested everything - it worked. So I started using "the process" each time I needed to back up.
Now it came to the point when I actually needed to restore. Fellow geeks know that all your live is in the calendar even your wife's birthday (just in case you forget you'll receive a email one week before and a SMS message every subsequent day - hard to miss). My fiddling with my phone emptied my entire calendar so you can imagine how I felt. After getting my breath back, and within 10 minutes my speech came back to normal - I was so proud of myself that just few days back I backed up my data.
But... as I said at the beginning - it never works.
I always export my entire set of calendars in bulk, so I basically download an archive with all my calendars. I tried to import it back - no luck. Nothing imported, no proper error message (shame on you Google), nothing.
Again not enough air in the room, speech slurred - you get the picture. Back to google, even though you're pretty angry with them, they are the only one who can get you around the web properly.
My first thought was that it is the UID - I had this problem before. Basically each event is assigned a UID so you won't import it twice, this feature should help you not too duplicate your events. After fiddling around with it it was clear is not the UID (I created a new calendar and tried to import the same .ics - didn't work).
After some search I came across this link http://severinghaus.org/projects/icv/ to check my .ics file integrity. Well it was corrupted:
Filename: Xyzxyzxyzxyzxyz_xyzxyzxyz@gmail.com.ics Size: 343058 bytes
Error: Error was: Error at line 1568: Illegal character in scheme name at index 0: Xxxxxx;X-NUM-GUESTS=0:mailto:xyzxyz@gmail.com Cause: Caused by: Illegal character in scheme name at index 0: Xxxxxx;X-NUM-GUESTS=0:mailto:xyzxyz@gmail.com Context for line 1568:
1565: UID:040000008200E00074C5B7101A82E00800000000A2698BE0CCF25088C44FD0777539CF6 1566: 5100000002099930B2F20B86B092F11F93D0ADF0E 1567: ATTENDEE;CUTYPE=INDIVIDUAL;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;CN=Oxana 1568: "Xxyxyxxx" Xxxxx;X-NUM-GUESTS=0:mailto:xyzxyz@gmail.com 1569: CREATED:20100220T103955Z 1570: LAST-MODIFIED:20100317T095102Z 1571: LOCATION:Reading If you've found a bug—say, a definitely valid iCalendar that generates errors—please check out the iCal4j bugs, forums, or feel free to contact me; minimal test cases are always appreciated!