Adafruit PiRTC - PCF8523 Real Time Clock for Raspberry Pi

This is a great battery-backed real time clock (RTC) that allows your Raspberry Pi project to keep track of time if the power is lost. Perfect for data-logging, clock-building, time-stamping, timers and alarms, etc. Equipped with PCF8523 RTC, it works great with the Raspberry Pi and has native kernel support.
Works perfectly with any Raspberry Pi (or similar single board linux computer) including the Pi 1, Pi 2, Pi 3, Pi Zero, A+, B+ etc.

Fully assembled & tested PCB plugs directly into your Pi's GPIO pins - No soldering required!

Will keep time for 5 years or more

Note: This product does not come with a CR1220 coin cell battery.
The PCF8523 is simple and inexpensive but not a high precision device. It may lose or gain a second or two per day. For a high-precision, temperature compensated alternative, please check out the DS3231 precision RTC.
For setting up your Raspberry Pi to use the PiRTC, check out Adafruit's detailed tutorial!
TECHNICAL DETAILS
Product Dimensions: 21.0mm x 20.0mm x 12.0mm / 0.8" x 0.8" x 0.5"
Product Weight: 2.2g / 0.1oz