RTC (DS3231) for Raspberry Pi

Extract from the data sheet:

• Highly Accurate RTC 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
• Accuracy ±2ppm from 0°C to +40°C
• Accuracy ±3.5ppm from -40°C to +85°C
• Digital Temp Sensor Output: ±3°C Accuracy
• Register for Aging Trim
• RST Output/Pushbutton Reset Debounce Input
• Simple Serial Interface Connects to Most Microcontrollers
• Fast (400kHz) I2C Interface
• Battery-Backup Input for Continuous Timekeeping
• Low Power Operation Extends Battery-Backup Run Time
• 3.3V Operation
• Operating Temperature Ranges: Commercial
• (0°C to +70°C) and Industrial (-40°C to +85°C)
• Underwriters Laboratories® (UL) Recognized