month of Sundays vs colloquialism

month of Sundays and colloquialism both are nouns.

Word	Noun	Adjective	Verb	Adverb
month of Sundays	Yes	No	No	No
colloquialism	Yes	No	No	No

month of Sundays (noun)	colloquialism (noun)
a time perceived as long	a colloquial expression; characteristic of spoken or written communication that seeks to imitate informal speech