2. Interest-free period: For consumer transactions, the interest-free repayment period is from the bank bookkeeping date to the due repayment date. Example: The billing date of Miss Zhang's credit card is 18 every month. She spent the money on August 19, 2009, and settled the bill on September 18, 2008. When she fully repaid the money on June 10 (August 65438-June, 2009 10), she enjoyed the longest interest-free period of 50 days.