https://learn.adafruit.com/adafruit-pcf8523-real-time-clock/real-time-clock
Real Time Clock | Adafruit PCF8523 Real Time Clock | Adafruit Learning System
This is a great battery-backed real time clock (RTC) that allows your microcontroller project to keep track of time even if it is reprogrammed, or if the power...
real time clockadafruitlearningsystem
https://www.adafruit.com/product/3386
Adafruit PiRTC - PCF8523 Real Time Clock for Raspberry Pi : Adafruit Industries, Unique & fun DIY...
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...
real time clockfor raspberry pi