Adafruit PiRTC DS3231

The best battery-backed real-time clock (RTC) you can get that allows your Raspberry Pi project to keep track of time if the power is lost. Perfect for data-logging, clock-building, NTP servers, time-stamping, timers and alarms, etc. Compatible with Raspberry Pi 1, Pi 2, Pi 3, Pi 4, Pi Zero, A+, B+ Fully assembled & tested PCB plugs directly into your Pi's GPIO pins - No soldering required! Will keep time for 5 years or more