eventide vs guest night

eventide and guest night both are nouns.

Word	Noun	Adjective	Verb	Adverb
eventide	Yes	No	No	No
guest night	Yes	No	No	No

As nouns, guest night is a hyponym of eventide; that is, guest night is a word with a more specific, narrower meaning than eventide:

eventide: the latter part of the day (the period of decreasing daylight from late afternoon until nightfall)
guest night: an evening when members of a club or college can bring their friends as guests

eventide (noun)	guest night (noun)
the latter part of the day (the period of decreasing daylight from late afternoon until nightfall)	an evening when members of a club or college can bring their friends as guests