The DS1307 serial real-time clock (RTC) is a lowpower, full binary-coded decimal (BCD) clock/calendar plus 56 bytes of NV SRAM. Address and data are transferred serially through an I2 C, bidirectional bus. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12- hour format with AM/PM indicator. The DS1307 has a built-in power-sense circuit that detects power failures and automatically switches to the backup supply. Timekeeping operation continues while the part operates from the backup supply. Usually CR2032 type coin cell is used for back up powersupply. The RTC interface is exteremely handy if any of your projects needs a real time clock which operates seamlessly even if the main powersupply is inconsistent. Remember the output is BCD encoded, hence you need to convert it to binary when using with micrcontrollers. Checkout our tutorials for various micrcontrollers below. The BCD however can be directly used to driver 7-segments with a decode like 7447.