These docs are for an old release.
Info on upgrading to v6
Event::setDates
Sets an event’s start date, end date, and allDay properties at the same time.
event.setDates( start, end, [ options ] )
start and end are parameters that must parse into a Date Objects. end can be null, in which case the end date will be cleared.
options is an optional plain object that can have the following property:
allDay—trueorfalse. will modify this event’sallDayproperty.
If there are other events that share the same groupId, those events’ dates will be similarly modified.