calendar week vs period of time

calendar week and period of time both are nouns.

Word	Noun	Adjective	Verb	Adverb
calendar week	Yes	No	No	No
period of time	Yes	No	No	No

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

calendar week: a period of seven consecutive days (usually reckoned to be from Sunday to Saturday, or from Monday to Sunday)
period of time: an amount of time

Other hypernyms of calendar week include period, time period.

calendar week (noun)	period of time (noun)
a period of seven consecutive days (usually reckoned to be from Sunday to Saturday, or from Monday to Sunday)	an amount of time