mid-February vs period of time

mid-February and period of time both are nouns.

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

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

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

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