An simple RTC (Real Time Clock) Shield for Arduino board with backup battery.

Simple DS1307 RTC Shield for Arduino boards...

Shopping List:
Amount | Part Type
2 - 1KΩ Resistor
1 - Arduino
1 - Crystal 32.768 KHz
1 - DS1307
1 - Generic male header - 2 pins
1 - CR2032 Battery Holder