mid-October vs period of time

mid-October and period of time both are nouns.

Word	Noun	Adjective	Verb	Adverb
mid-October	Yes	No	No	No
period of time	Yes	No	No	No

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

Other hypernyms of mid-October include period, time period.

mid-October (noun)	period of time (noun)
the middle part of October	an amount of time