departure time vs point in time

departure time and point in time both are nouns.

Word	Noun	Adjective	Verb	Adverb
departure time	Yes	No	No	No
point in time	Yes	No	No	No

As nouns, point in time is a hypernym of departure time; that is, point in time is a word with a broader meaning than departure time:

departure time: the time at which a public conveyance is scheduled to depart from a given point of origin
point in time: an instant of time

Other hypernyms of departure time include point.

departure time (noun)	point in time (noun)
the time at which a public conveyance is scheduled to depart from a given point of origin	an instant of time