This is the 8376th most frequent Dutch word.
gisterenavond
"Last night."
'Gisterenavond' is used here as an adverb to specify the time when the action took place.
Gisterenavond keek ik naar een film.
Last night I watched a movie.
In this sentence, 'gisterenavond' serves as an adverb indicating the time period mentioned.
Gisterenavond was het erg koud buiten.
Last night, it was very cold outside.
'Gisterenavond' is utilized in this question to point to the specific time when the event (eating) occurred.