Whether a payment is considered late or not is generally determined by the terms of your credit card account agreement.  If your payment is received prior to the due date included on your statement, your payment will not be considered late. 

The Credit CARD Act requires that if you mail your payment and the due date falls on a day when the lender does not accept or receive mailed payments, then a payment will be considered timely if it is received by the lender prior to the cut-off time on the next business day.