TOPIC: [SOLVED] Upgraded to 2.8 - Calendar not loading events

I had the same issue.
I found that the file
/components/com_dtregister/assets/js/calendar/wdCalendar_lang_US.php
was returning php warning errors therefore causing java script errors in the browser.
I check the Global configuration setting in Joomla under Server-> error reporting and that was set to "default"
I changed this to "none" and it is now working.

I hope that helps others.