The start() method returns the current event start value or sets a new one.
DayPilot.Event.start()
DayPilot.Event.start(newStart)The new value is applied when you call DayPilot.Scheduler.events.update().
newStart (DayPilot.Date) - new event start value.
Call the method without parameters to read the current start value. Call it with a DayPilot.Date value to update the event object before saving it back to the control.
const oldStart = e.start();
e.start(new DayPilot.Date("2015-10-01T00:00:00"));