Doomsday Method vs Aritmo

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/

Train your brain to calculate faster with short, structured mental math lessons. Aritmo teaches rapid calculation techniques through focused lessons, interactive practice, and gamified challenges. Instead of memorizing random tricks, you learn step-by-step methods for solving arithmetic problems more efficiently in your head. LEARN MENTAL MATH STEP BY STEP Aritmo is designed to help you build real calculation skills through progressive courses and practice exercises. In this first version, Aritmo includes two main learning paths: • Basic Multiplication Learn the Trachtenberg method for rapid multiplication with numbers from 2 to 11. This course introduces the core patterns and rules used to multiply faster mentally. • General Multiplication Learn a broader multiplication method for solving more flexible multiplication problems. This course is available with an active subscription. The app clearly identifies which content is included and which content requires a subscription before purchase. PRACTICE WITH SHORT DAILY LESSONS Each concept is broken into simple lessons that can be completed in a few minutes. You can learn a method, practice it immediately, and repeat challenges to build speed and confidence over time. Aritmo helps you practice: • Fast multiplication techniques • Mental arithmetic without a calculator • Number patterns that simplify calculations • Focused repetition for stronger recall • Progressive exercises that increase in difficulty GAMIFIED BRAIN TRAINING Aritmo turns mental math practice into a structured daily challenge. You can: • Progress through lessons • Complete practice exercises • Build learning streaks • Track your progress • Improve your speed through repetition WHO IS ARITMO FOR? Aritmo is useful for: • Students who want stronger arithmetic skills • Adults who want to sharpen their mental calculation ability • Puzzle and brain-training enthusiasts • Anyone curious about rapid mental math methods • Learners who want structured practice instead of random math tricks SUBSCRIPTION INFORMATION Aritmo offers optional in-app purchases. The Basic Multiplication course is available in the app. The General Multiplication course requires an active subscription. Subscription availability and terms are shown clearly in the app before purchase and are managed through your Apple ID. You can use Aritmo to start learning mental multiplication techniques and upgrade only if you want access to the additional subscription course. Start training your mental math skills with Aritmo. Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://melbot.com.br/privacy.html