根据我自己的经验,以上的情况都可能发生 , depend on the billing system of the payee. 有的是以到款日来决定你是否迟付了,计算利息;有的则在它的下一个billing date, 看是否有没有欠款,所以你有可能在due date 和 billing date 之间打一个时间差,躲过利息。
还要赞一句TD,午夜之前网上付款,下一个工作日就能到。
至于信用,credit card companies report frequentlly to the credit bureaus;your late payment might get recorded and then updated in the next reporting cycle. Arreares less than 30 days will not likely affect your credit score.