I recently made a purchase and canceled it shortly after, because I did it by mistake, the seller accepted it, the cancellation exists, but there is no refund in the order.
There is no deadline that I know about in this instance. If the cancellation has been accepted, and the purchase cancelled, eBay will refund the money to your payment source. I do not know if it matters if it was a domestic purchase or one from an international seller. It is not going to be instant, as I don't think eBay refunds any faster than they give the money to a seller for a sale in the first place.
If your seller is "new" he/she may be required to front the money for the cancellation refund, for eBay will not use any funds on hold due to the seller being new. Typically, you would get notice if there was a problem. Look for the refund in the account you used to pay.
