Change default event notification sound

From https://discussions.apple.com/message/28106368#message28106368:

Edit EventAllDayAlarms.icsalarm and EventTimedAlarms.icsalarm for the relevant calendar under ~/Library/Calendars. Change ATTACH;VALUE=URI:Basso to the name of the new sound.

Note files are overwritten when you change calendar preferences.

Sound file may need to be in /System/Library/Sounds, which won’t work under SIP.

Why is this so hard?!?

Create local-only calendars

http://apple.stackexchange.com/questions/119813/how-to-set-up-a-local-calendar-while-using-icloud-for-other-calendar-on-maverick

In short:

• Switch off Calendars for all accounts in Internet Accounts that use them.
• Add a new calendar (File ▷ New Calendar ▷ On My Mac).

Re-enable calendars in all accounts that use them.