Doomsday Method vs Doomsday Practice

Someone tells you the date they were born. You tell them it was a Monday. That is a real skill, it takes about a week to learn, and this app teaches it end to end. The Doomsday algorithm — invented by the mathematician John Conway — turns any date into its weekday using arithmetic small enough to finish while someone is still saying the date. No lookup. No phone. No calendar. LEARN 48 lessons across 11 chapters, in three parts 178 checkpoint questions. You answer in your head, then check yourself against the worked reasoning — nothing is graded, and nothing is rushed Interactive calendars, anchor tables and step-by-step walkthroughs inside the lessons themselves Mnemonics that stick: 4/4, 6/6, 8/8, 10/10, 12/12, and "9-to-5 at the 7-Eleven" Six different ways to work the year offset. Pick the one your head likes, and every worked explanation in the app is rewritten in it Seven Extras: why the method works, Easter and the computus, the Julian calendar, Conway's own shortcuts, the record holders, and full reference tables A cheatsheet with every anchor and every offset on one screen TRAIN 10 drills: weekday numbers, counting in sevens, leap years, century anchors, the year offset, month doomsdays, day counting, reverse dates, Julian dates and Easter Five stars a drill, earned by answering cleanly — right, and inside that drill's target time Nothing cuts you off mid-question, and training never costs you rating PLAY Classic — endless real dates, at your own pace, with no clock at all Daily Challenge — five dates drawn from the day itself, identical for every player on earth, one attempt a day Time Attack — two minutes, as many dates as you can, ten seconds off for every miss Choose your range: 2000–2099, 1800–2199, or the whole Gregorian calendar from 1583 to 2599 YOUR PROGRESS A Doomsday Rating that rises when you are right and quick, and never pays for a guess Accuracy and speed over time, your rating history, and a 12-week activity calendar Game Center leaderboards for today's challenge and the global rating, friends included BUILT PROPERLY No account, no sign-up, no ads Works offline Every number in every lesson is re-derived by a checker that shares no code with the app, so an explanation cannot drift from the answer it gives Analytics are opt-in, pseudonymous and on EU servers. You are asked once, and can change your mind any time in Settings Coming from the old Doomsday Method? Your history is imported and replayed answer by answer, so your chart reaches back and your rating arrives honest Start free. One optional purchase opens the rest — one payment, not a subscription. --- EULA: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Doomsday Practice helps you master the Doomsday algorithm: a mental math technique for calculating the day of the week for any date in your head. LEARN Step-by-step lessons break the algorithm into digestible pieces. Understand the anchor days, memorize the Doomsday dates, and build a reliable mental framework at your own pace. PRACTICE Drill random dates across any year or century. Get instant feedback, track your accuracy, and build speed through repetition. REVIEW A clean reference sheet keeps the key rules and mnemonics at your fingertips while you're still building fluency. TRACK YOUR PROGRESS Streaks and stats keep you accountable. Watch your accuracy and response time improve over time. Whether you're a mental math enthusiast, a memory competitor, or just want a party trick that actually impresses people: Doomsday Practice gets you there.