Admin UI has timezone issues

Report on mailing list by Todd Porteous, Mohd Assidiq () and djeronimo in IRC. Unclear what is going on, or if they are even experiencing the same issue, but it sounds like they are: Attempts to schedule an event in the current day give a scheduling error that the event has already ended.

Additional info:
-djeronimo reports his date widget is rendering with Monday as the first day of the week