The settlement period starts on the 20th of the month and ends on the 20th of the following month.
On the 20th of each month, a bill is issued for the total of all the purchases you made with your credit card during this period. If the 20th is not a business day, it will be issued on the preceding business day.
You can choose the bill charge date: the 21st of the settlement month or the 5th of the following month, and you can change it at any time. Although if you opted for deferred payments, you will have to pay interest from the settlement date until the payment date.
If you change the debit date before the 20th of the month, it will take effect in that month's settlement. If you change it between day 20 and 30 of the month, the change will take effect in the settlement for the following month.
Deferred payments are settled on the last business day of the month. This day (30th or 31st), the bill corresponding to the settlement is issued, and then charged to the account on the 5th of the following month.