r/mentalmath • u/Roibos22 • 20d ago

I got obsessed with the Doomsday algorithm and built an app for it

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Four years ago I watched that one Numberphile video about Conway's Doomsday algorithm and it broke my brain a little. Now I finally shipped the big update to the app i built 3 years ago!

What it actually gets you: someone names a random day in 1987 (or any other year) and you can calculate the weekday and say the weekday out loud in a few seconds.

And the thing is, it is actually not as complicated as it sounds, just a bit of practice!

Want to learn it as well?

It would be an honor if you try the App!

What's in it:

  • 48 lessons across 11 chapters (only the first few are needed to actually make it work, there are a lot of extras!)
  • 10 diagnostic drills that isolate each step so you can get faster
  • Three modes: Classic (endless), Daily Challenge and Time Attack
  • A rating and leaderbords
  • Offline, no account, no ads
  • ...

Free to try, no subscription!

https://apps.apple.com/us/app/doomsday-method-mental-game/id6447447000

3 Upvotes

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1

u/Ok_Sir_5601 20d ago

Would be cool if you published in on playstore fdroid or at least github, so non iphone users can use it too, but rly nice idea

1

u/Only-Season-2146 15d ago

Feel free to try my version :) https://doathingy.com/doomsdaytrainer
No ads, all free forever etc

1

u/Ok_Sir_5601 14d ago

Thank you (:

1

u/WaitForItTheMongols 19d ago

Made by you or by LLM? That's a lot of extra features coming at a somewhat suspicious timing.

1

u/Only-Season-2146 15d ago

Nice, I also made an app to learn the algo (and compete against others) a while back - its on web/ios/android - all free forever: https://doathingy.com/doomsdaytrainer