springtime vs time of year

springtime and time of year both are nouns.

Word	Noun	Adjective	Verb	Adverb
springtime	Yes	No	No	No
time of year	Yes	No	No	No

As nouns, time of year is a hypernym of springtime; that is, time of year is a word with a broader meaning than springtime:

springtime: the season of growth; spring; the beginning of spring
time of year: one of the natural periods into which the year is divided by the equinoxes and solstices or atmospheric conditions

Other hypernyms of springtime include season.

springtime (noun)	time of year (noun)
the season of growth; spring; the beginning of spring	one of the natural periods into which the year is divided by the equinoxes and solstices or atmospheric conditions