I'm double-checking it:
She goes swimming on Tuesday.
Is it the same as "She goes swimming on Tuesdays"?
Generally, do we necessarily pluralize the days of the week if something is frequently done on any day of the week?
I guess the answer will be "it should be plural; Tuesdays". Then what about this: "We don't work on Thursday?". Here, it is perfectly understood that they don't work on any Thursday during the month. Right? But no plurality. Why? Why can I use singularity of the day here, which refers to the frequent occurrence of something, but I can't do the same in the swimming example. What's the technical answer?