festival vs period of time

festival and period of time both are nouns.

Word	Noun	Adjective	Verb	Adverb
festival	Yes	No	No	No
period of time	Yes	No	No	No

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

Other hypernyms of festival include period, time period.

festival (noun)	period of time (noun)
an organized series of acts and performances (usually in one place)	an amount of time
a day or period of time set aside for feasting and celebration