My mother seldom watches TV at night.The use of the genitive here in “des Abends” feels odd, the way the "of a night…Is 'poetical… I’ve never encountered a time expression with a definite article before and would love to be enlightened as to its use.
Once again, correct but very old fashioned and yes, maybe poetical.
Much more common:
“Meine Mutter sieht abends selten fern.”
“Meine Mutter sieht am Abend selten fern.”