I found a grammar book that states the following:
(Grammar In Use Intermediate by Cambridge unit 18 pg.36 Present Tenses )
Which means that it is OK to use the simple present form to describe the future with fixed schedules.
But is it also OK to use the simple present to talk about fixed schedules that are not future?
Here is an example of a Japanese Jr. High English textbook (Level 1 New Horizon by Tokyo Shoseki 23rd year of Heisei Unit 3 Pg. 31)
In this example it says,
A: Do you come to school every day?
B: No, I don't. I come to school on Tuesday and Friday.
But if she only comes on Tuesdays would it be OK to say,
I come to school on Tuesday
Or should she say,
I come to school on Tuesdays?
I am not looking for an answer that is an opinion. I need to have a sited text from a legitimate published work that has an example of using the simple present with a day of the week in the singular form. This has to do with a student's paper. I cannot grade it based on conjecture.