Still no acceptable answer?
I am experiencing the exact same error. I have defined:
Additionally I confirmed with a database browser there are no meetings with start_time or end_time as undefined, null, or an empty string, or even any type other than Date(). Everything on the calendar works, but when I hit the save button KendoUI complains about getTimezoneOffset of null, pointing only to minified files, and the page must be reloaded. The meeting does save, however.
All other CRUD endpoints are hooked up and work correctly. Even a decent workaround would be acceptable.
I won't get my hopes up though, since this question has been open since October of 2014.