"On a Wednesday?"
Translation:Un mercredi ?
Oops, "on" isn't a verb, it's a preposition! What I meant was, isn't the sentence missing some information by not having a preposition?
Your example makes sense, it just seems to me like the sentence would be more complete if it was "A un dimanche?". Maybe I just need to accept that that's the way it's done in French.
"à un dimanche" would mean that you wish to see the person on a unspecified Sunday (and it would be quite awkward, actually, to say that) = See you on a Sunday. "à dimanche" means "See you on Sunday". It's different from "On a Sunday" like I explained before. Hope everythin's fine right now :)