In this project, PCF85063ATL CMOS Real-time Clock (RTC) is used as the time generator. This provides year, month, day, weekday, hours, minutes, and seconds based on a 32.768 kHz quartz crystal. A one-farad super capacitor combined with a low forward voltage diode can be used as a standby or backup supply. The output clock pulse of the PCF85063ATL is fed to the ATMEGA328P microcontroller.
schematic and more www.digikey.com/schemeit#wp0