Here's some of the cardmember agreement for charge cards
Payment of the New Balance is due upon receipt of your
statement.
If you do not pay the Amount Due on a billing statement before the 10th day after the next Closing Date, you will be charged a late payment fee. This fee will be $25, or $35 for a subsequent late payment in the next 6 billing periods. In addition, if you do not pay an Amount Due for two billing periods in a row, we will charge the greater of $35 or 2.99% of the amount past due.
The "please pay by" is not referenced in the agreement. However, it is due upon reciept and how long you take to pay would likely be evaluated over time as part of an internal exposure calculation for setting spending limits.
I have reestablished credit over the last couple years