May

If you like the program, consider supporting the developer by purchasing unDisturber Donation Package.
https://play.google.com/store/apps/details?id=com.stanislav.disturberDonationPackage

This app is a memory training aid, which helps you to train figuring out the weekday of any date literally at once without resorting to a calendar. For example, someone asks you: "Which day is Sep 2, 2021?" And you, without a pause, right away can say that it is Thursday. It may sound difficult, but actually this trick is quite easy. There are a number of memorizing systems, which allow for doing that. Any memory athlete knows them quite well.
For example this:
https://lifehacker.com/how-to-quickly-figure-out-the-day-of-the-week-any-date-5848651

Or this:
http://gmmentalgym.blogspot.com/2011/03/day-of-week-for-any-date-revised.html
I guess this app might also be useful as one of the tools in integrated rehabilitation programs for people, recovering from stroke, or some other kind of brain damage.
It just offers you a random date from a chosen range and you have to figure out which weekday it is. The app will also give back some statistics for performance improvement. Mastering such a skill will not only make life more convenient, since there will be no need to address a calendar every so often, but also will offer a perfect mental training, keeping brain active and robust. Let alone the fact that you will amaze your friends a great deal.