It looks to me that both are correct. Sunday is understood to be a particular place in the week or in calendar time, hence on. Sunday evening and sunday can both be.
Very Strong Winds on Sunday
Besides, if you say you do something on sunday (s), monday (s), etc. Only on sunday did i remember that i was supposed to have sent the report on friday morning. , it also conveys the sense that you do it on every sunday, monday,.
The deadline was over at the point of the.
Sunday's is possessive in nature when you use the apostrophe. Jesse takes the train in the morning on sunday. Or jesse takes the train in the morning of sunday. Use sundays instead, unless you know someone named sunday.
