<< This thread began as an off-topic but almost on-topic topic in <Are you><Do you> open 24 hours? >> That's interesting. I presume this is a difference between American and Irish English, but if I said "What time are you open on Saturday?" I would mean "At what time do you open on Saturday?" If I wanted to know the space of time, I would have to say "What times are you open on Saturday?" We would hardly ever leave out the on from "on Saturday".