Early departure...
Departure simply means leaving. Whether leaving a place or an event or whatever, the mainstay is the leaving aspect.
So an early departure wouldean leave earlier than scheduled. When a person leaves before the time assigned for him to leave, we will say he has departed early.
This happens a lot of times, mostly in events. Probably because of boredom or another engagement but the reason does not really matter at this point, we are only considering the early departure.
Another example is a the plane departing earlier than scheduled, slot of folks would miss that one. An early departure is common to people all the time.
Thank you for your time...