Bookkeeping day: it is to summarize all the consumption in this bookkeeping period and see how much you spent and how much you paid back in this bookkeeping period.
Repayment period: refers to the latest date stipulated by the issuing bank that the cardholder should repay the full repayment or the minimum repayment amount. The due repayment date is the date after the bank generates the bill, plus the interest-free repayment days.
The interest-free repayment period varies according to the regulations of each bank. The shortest is from the billing date to the final repayment date, and the longest is from the day after the billing date to the final repayment date of next month. If the billing date is 1 day and the final repayment date is 20 days, the shortest is 20 days and the longest is 50 days.
During the interest-free repayment period, as long as the current repayment amount on the current statement is fully paid off, there is no need to pay interest (advance cash does not enjoy interest-free concessions). If you don't repay the loan during the interest-free repayment period, you will have to charge interest and late fees.