I used to go out on sundays

[zoobinshid]

Hello everyone,
Would you please tell me if this sentence is right or not?

( I used to go out on sundays )

Or we have to say every sunday?I mean can we add plural ( s ) to days of week?

Thanks in advance,

[Temico]

There is a slight difference between:-
a) I used to go out on Sundays.
b) I used to go out every Sunday.

(a) means that you used to go out on Sundays but not necessarily every Sunday.
(b) means that you used to go out each and every Sunday without missing a single one.