pastime vs diversion

pastime and diversion both are nouns.

Word	Noun	Adjective	Verb	Adverb
pastime	Yes	No	No	No
diversion	Yes	No	No	No

As nouns, diversion is a hypernym of pastime; that is, diversion is a word with a broader meaning than pastime:

pastime: a diversion that occupies one's time and thoughts (usually pleasantly)
diversion: an activity that diverts or amuses or stimulates

Other hypernyms of pastime include recreation.

pastime (noun)	diversion (noun)
a diversion that occupies one's time and thoughts (usually pleasantly)	an activity that diverts or amuses or stimulates
	a turning aside (of your course or attention or concern)
	an attack calculated to draw enemy defense away from the point of the principal attack