noun, adverb
Used as both a noun and a time adverbial. With dates and plans, 土曜日に is common, but 土曜日 alone can also mark when something happens.
土曜日は仕事が休みです。
I have Saturday off from work.
土曜日に友だちと映画を見ます。
I’m going to see a movie with a friend on Saturday.