“Digital clocks usually have very confusing user interfaces to set the time. They require holding down buttons to go between different modes, and often you can only increment the time, for example, if you want to decrement one minute, you need to press a button 59 times. This was the main reason I created this clock.
This clock is based on an Arduino NANO, since that was what I had laying around, but almost any Arduino would work. I use a DS3232RCT module to keep track of the time. Since it has a battery backup it keeps the time during power failures, or if the clock is moved to a different position/power outlet. The time is shown on a serial LED display based on the TM1637 chip. Both the display module and the RCT module are available for cheap on eBay. My experience is that those cheap DS3232RCT modules are actually a lot better at keeping the time than most Digital clocks you can buy.
I have found that those cheap DS3232RCT modules are actually a lot better at keeping the time than most commercial digital clocks. The battery lasts for years, and they drift less than one minute over a period of one year.”