How many day do you to return a new car in Virginia?

No US state has an automatic right to return a new car. Once the contract's signed, it's a done deal; you don't get to change your mind and get a mulligan.

In some (but not all) states, dealers are required to offer you an option to purchase this right at the time you buy the car. Note that this is an OPTION to PURCHASE the right, you don't automatically get it for free even in those states.

A dealer may, at their option, allow you to return a car you've just purchased as a goodwill gesture even if they're not legally required to. A dealer might have specific policies about this, or it could be up to the manager/owner whether to allow it or not on a case-by-case basis. Since this basically boils down to "how much do they want to make you personally happy", you should probably start by being REALLY polite when you ask. They might be more inclined to allow it if you're telling them "I'd like to cancel this contract and buy that other car you have over there instead," since that way they're not totally losing out on a sale.

The bottom line is: check your contract. It almost certainly states very clearly that there is no automatic right of rescission. If it says something else, then whatever it says goes.