A method for recording the use time of a computer system is disclosed. The method includes storing the last power-on time of the computer system before shipping (the base use time) and a time variable in the basic input/output system (BIOS). Moreover, the time variable is increased every time a periodic interrupt takes place. The total use time of the computer system is then calculated according to the time variable and the periods of the periodic interrupt. Thus, the base use time and the total use time can be shown on the BIOS setup menu. Therefore, the method is able to achieve the purpose of recording the time and date when the computer system is turned on for the last time just before shipping and the total operating time of the computer system after shipping.