Hi Mike,
As far as I can remember, the calendar code itself is compatible with 1.2.1, but I think you will be facing other problems:
- mdl_events table?
- Since it has moved to blocks, you 'll need to resurrect calendar_print_side_blocks()
- Might be other things that don't come to mind right now
On the other hand, as long as you have the correct mdl_event table and since it was developed with "ease of insertion" in mind, you could dig up the old installation instructions and give it a shot. It's 100% safe, you can always comment out calendar_print_side_blocks() if something's not working correctly. So if you 're feeling adventurous...
Good luck!
Jon