The accounting system of a savings bank is not materially different from that of other banks except in the matter of keeping the interest accounts of the depositors. Most banks compute interest at semi-annual, quarterly, or in some cases monthly periods. After the trustees declare the interest rate for the quarter or half-year, the amount is computed for each account. Generally interest is allowed only on the amount running undisturbed through the period. Deposits made after the beginning of a period will not bear interest until the next interest date, and withdrawals during the period forfeit the interest accrued since the last dividend. Some banks calculate interest from the first of each month succeeding the deposit, and even allow interest on deposits made within three, five or ten days after the dividend day. At the end of each dividend period the interest is entered in the ledgers in red ink, and if not drawn out it is added to the depositor's balance and begins to bear interest itself. The first time the pass book is presented after an interest period the accrued interest is entered in red ink. The rules or by-laws made by savings banks regarding deposits, withdrawals and interest are printed in the pass book, and unless unreasonable they form a contract between the depositor and the bank.