DS1307 Real-time clock module
Supply 5V DC
Completely Manages All Timekeeping Functions
Real-Time Clock Counts Seconds, Minutes, Hours, Date of the Month, Month, Day of the Week, and Year with Leap-Year Compensation Valid Up to 2100
56-Byte, Battery-Backed, General-Purpose RAM with Unlimited Writes
Programmable Square-Wave Output Signal
Simple Serial Port Interfaces to Most Microcontrollers
I2C Serial Interface
Low Power Operation Extends Battery Backup Run Time