I just saw this thread and got completely confused. What is the "s" at the end of some words and where does it go when talking about multiples?
Since the subject remains Sunday, the verb remains works (3rd-person singular present).
How can a day of the week be third person singular?
Please note, I was taught English by reading good books (this was how UK schools worked in the 70s and 80s), so despite being able to talk/write good English (when I remember) my understanding of why is 0.
I follow most of the answers but this was simply a WTF moment.