Train your mental abilities and impress your friend by learning to use the Doomsday Algorithm! This simple and fast set of rules will let you calculate the day on which any date fell! Currently with CLI, but a GUI is in early stage.
If you choose to use the source code as-is, simply unzip/clone the repository and make background.pyw as a startup script.
The only dependency is Python 3.
Alternatively, you can download the binaries from this folder (currently only on Windows), and make trainer.exe as a startup script.
The program will ask you a date at login and every hour; your answer time is measured and logged in average.log, and a data analyser is under development. Good training!