Q: Clearing Calendar Cache when Calendar won't close down.

I'm running OS X Yosemite 10.10.5 on my Macbook Pro. I've copied and pasted data from an outside source like the internet into new Calendar event and suddenly Calendar program freezes once I paste in the excessively long entry. Now my Calendar program is stuck on this one entry and refuses to close even when I try to force close the app. I can't even Shut down my computer because Calendar will not close down. This scenario has happened to me 3 separate times and it was difficult to resolve because I had forgotten the answer as the time spans between events were too great. And let's face it when you resolve an infrequent issue you generally want to forget about it. So here is the solution that worked for me:

Go to the Finder menu...and select Go whilst pressing down the Option key this will give you an additional option on the submenu called Library.

Select Library which will open another folder

Within the Library folder select calendar cache typically you'll find 3 files made today titled:

     Calendar Cache

     Calendar Cache-shm

     Calendar Cache-wal 

Select and drag these 3 files to the Trash

Close the Calendar App using the force quit process

Restart your computer

Open Calendar and find the offending entry and don't open it just click once and delete it. If you open it you'll have to go through the cache clearing process again. Hope this helps someone.