Real time clocks (rtc), as the name recommends are clock modules. The ds1307 real time clock (rtc) ic is an 8 pin device using an i2c interface. The real time clock ds1307 rtc i2c module with battery is a low-power clock/calendar with 56 bytes of battery backup sram. The clock/calendar provides seconds, minutes, hours, day, date, month and year qualified data. The end date of each month is automatically adjusted, especially for months with less than 31 days.