FullCalendar has a option for this, ignoreTimezone (see: http://arshaw.com/fullcalendar/docs/event_data/ignoreTimezone/ ), just make sure this is set to true (which it is by default*) and the user will see the same time that the server sends, regardless of user's timezone.
(*personally I think the default is wrong, and the developer seems to acknowledge that in the docs, so it'd be worth setting explicitly.)