Battery Backed I2C Real Time Clock/Calendar with EEPROM and Unique ID in SOIC-8 Package - 

MCP79410-I/SN is a battery-backed I2C real-time clock/calendar with SRAM, EEPROM, and protected EEPROM. It is a 1.8V - 5.5V, unprogrammed I²C serial RTCC that tracks time using internal counters for hours, minutes, seconds, days, months, years, days, and weeks. Alarms can be configured on all counters up to and including months. For usage and configuration, the MCP7941X supports I²C communications up to 400KHz. The open-drain, multi-functional output can be configured to assert on an alarm match, to output a selectable frequency square wave, or as a general-purpose output. It is designed to operate using a 32.768KHz tuning fork crystal with external crystal load capacitors. SRAM and timekeeping circuitry are powered from the backup supply when the main power is lost, allowing the device to maintain accurate time and the SRAM contents. The times when the device switches over to the backup supply and when primary power returns are both logged by the power-fail timestamp.