Question: Fix for "On My Mac" calendars not available when using iCloud
I researched this one for a while and found all kinds of answers (even from Apple) that did not work so I decided to post how I fixed it.
Problem: Cannot add an "Open file" alert in a calendar event. Adding the alert gets automatically deleted after applying the setting.
The root cause was that I tried adding the Alert to an iCloud calendar, which, as I found out, doesn't work. (Apple, you should just not allow us to select the option in that case).
The proposed fix was to add an "On My Mac" Calendar, but every time I tried, the calendar would get automatically created in iCloud. If I disabled iCloud, it would add the calendar properly but would convert it to an iCloud calendar as soon as I logged back in.
1. Unselect all of your iCloud Calendars:
2. Right click on the white space below all of your calendars and select New Calendar
3. An Untitled calendar shows up at the top in an added section called On My Mac
4. Add all of your iCloud calendars checkmark back in and you are good to go.
You can now add an event in your new On My Mac calendar and schedule an alert to open a file, and in my case, have it repeated daily.
I hope this was useful!
iMac Intel 2.16Ghz, Mac OS X (10.6.1)