This is a great PCB project made by Giannis Vasilakis
and posted on Instructables. A DIY guide that will show you how to make your own Arduino aquarium auto lighting system. In this project Giannis decided to make his own PCB that is based on Arduino UNO microcontroller - Atmega328p. On the full post
you will find the electronic schematic with PCB layout so you can easily produce it.
The current time can be set for the first time (or when the coin battery is low) via the serial monitor. You can change the lighting change time or led color from code.