Sets an event’s start date.
event.setStart( date, [ options ] )
date is something that must parse into a Date Object.
options is an optional plain object that can have the following property:
maintainDuration— if set to
true, the event’s
endwill also be adjusted in order to keep the same duration
If you’d like to set both the
end at the same time, use setDates instead.
If there are other events that share the same
groupId, those events’ dates will be similarly modified.