eve vs twenty-four hour period

eve and twenty-four hour period both are nouns.

Word	Noun	Adjective	Verb	Adverb
eve	Yes	No	No	No
twenty-four hour period	Yes	No	No	No

As nouns, twenty-four hour period is a hypernym of eve; that is, twenty-four hour period is a word with a broader meaning than eve:

eve: the day before
twenty-four hour period: time for Earth to make a complete rotation on its axis

Other hypernyms of eve include 24-hour interval, day, mean solar day, solar day, twenty-four hours.

eve (noun)	twenty-four hour period (noun)
the latter part of the day (the period of decreasing daylight from late afternoon until nightfall)	time for Earth to make a complete rotation on its axis
the day before
the period immediately before something