The repayment period and billing date of different bank credit cards are different. If the billing date and repayment date of the bank credit card are 20 days. 17 bookkeeping date, 7th of next month (6th in case of big month) repayment date. If you spend on 18, it will be charged to the bill of 17 next month, and the final repayment date is the 7th of next month, so you can enjoy the longest interest-free period.