heyday vs time period

heyday and time period both are nouns.

Word	Noun	Adjective	Verb	Adverb
heyday	Yes	No	No	No
time period	Yes	No	No	No

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

Other hypernyms of heyday include period, period of time.

heyday (noun)	time period (noun)
the period of greatest prosperity or productivity	an amount of time