This cute little Realt-Time clock module features a DS1302 

trickle-charge Timekeeping Chip and is powered by a 32.768kHz Crystal and a battery holder for a CR2032 Button Battery. It can also be powered directly from a backup power source.

SPECIFICATION

DS1302 trickle-charge Timekeeping Chip

• 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
• 31 x 8 Battery-Backed General-Purpose RAM
• Simple Serial Port Interfaces to Most Microcontrollers
• Simple 3-Wire Interface o TTL-Compatible (VCC = 5V)
• Single-Byte or Multiple-Byte (Burst Mode) Data Transfer for reading or writing of Clock or RAM Data
• Low Power Operation Extends Battery Backup Run Time
• 2.0V to 5.5V Full Operation
• Uses Less Than 300nA at 2.0V

Board

• DS1302 chip
• Battery Holder
• DS1302 Chip breakout PINs for the 3-wire interface and additional  backup power
• 32.768kHz Crystal