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 DS1307 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.

DATA SHEET : https://5.imimg.com/data5/UM/UC/MY-1833510/ds1307-i2c-real-time-clock-module.pdf