Download eagle arduino 8.5.1 final full version
The circuit is based in an Arduino Nano, but, it could be constructed arround an Arduino Uno or any compatible board, even with and Atmega328 and few components. The principals peripherals are a DS3231 RTC module and an SD card reader. The DS3231 is connected to the processor via I2C bus (SDA -> A4 and SCL -> A5 pins in Arduino, plus power).