# Doomsday Trainer — Know the day for any date! > Calculate the day of the week for any date using various algorithms. (iPhone/iPad app by Maarten Claessen.) - Source: https://appshunter.io/ios/app/doomsday-trainer/id6760719687 (this page in markdown: same URL + `.md`) - Developer: [Maarten Claessen](https://appshunter.io/developer/1885901059) - Category: Education, Games, Puzzle, Trivia - Price: Free - Rating: 5.00/5 from 1 App Store ratings - Age rating: 4+ - Requires: iOS 15.0 · 15 MB - Languages: American English - Released: 2026-03-27 - Data updated: 2026-08-30 - Monetization: free - User reviews in markdown: https://appshunter.io/ios/app/doomsday-trainer/id6760719687/reviews.md ## What is Doomsday Trainer? Master the Doomsday Algorithm — calculate the day of the week for any date in history in seconds. PLAY Build your streak and beat the clock. Every correct answer adds to your streak; one wrong answer ends it. Compete on the global leaderboard for Longest Streak and Fastest Average Speed. BATTLE Challenge a real opponent to a live 1-on-1 race. Five dates, fastest and most accurate player wins. Elo-based ranking tracks your competitive record. TRAIN Six methods to choose from: • Doomsday — the classic anchor-day approach • Odd + 11 — the Fong-Walters mental shortcut • The Wollin Shortcut — a memory-based system using vectorized doomsdays, the Square Knot Rule, and the Wollin Calamity Table (by u/Nillows) • Conway's Method — the original algorithm by John Conway • Mod 28 — reduce any year to under 28 before calculating • Custom Mode — pick your own date range, century, or decade DRILL Targeted practice for each component: months, centuries, years, mod 7 arithmetic, and the full Wollin Shortcut drill suite. TUTORIAL New to the algorithm? The built-in tutorial walks you through everything step by step. ## Key features - Doomsday Algorithm calculation - Timed streak challenges - 1-on-1 live battles - Multiple training methods - Targeted component drills - Step-by-step tutorial ## Frequently asked questions about Doomsday Trainer ### What is the Doomsday Algorithm? The Doomsday Algorithm is a method for calculating the day of the week for any given date. Doomsday Trainer allows you to master this algorithm through various practice modes and challenges. ### How does Doomsday Trainer help with learning? Doomsday Trainer offers a built-in tutorial, targeted drills for specific components like months and centuries, and multiple training methods to cater to different learning styles. ### Can I compete with other users on Doomsday Trainer? Yes, Doomsday Trainer features a live 1-on-1 battle mode where you can challenge opponents. It also includes global leaderboards for longest streak and fastest average speed. ### What are the different training methods available in Doomsday Trainer? Doomsday Trainer supports six methods: the classic Doomsday, Odd + 11, The Wollin Shortcut, Conway's Method, Mod 28, and a Custom Mode for personalized practice. ### Is Doomsday Trainer suitable for all ages? Doomsday Trainer has an age rating of 4+, making it accessible for a wide range of users interested in learning and practicing date calculations. ### How often is Doomsday Trainer updated? The latest version of Doomsday Trainer is 1.3.6, and it was last updated on April 20, 2026. Updates typically bring improvements and new features. ### Does Doomsday Trainer have ads? No, Doomsday Trainer is ad-free, allowing for an uninterrupted learning and practice experience. ### What devices does Doomsday Trainer support? Doomsday Trainer is available on iPhone, iPad, and iPod devices. ## Version history (last 5 releases) ### 1.3.7 — 2026-08-27 Various bug fixes ### 1.3.6 — 2026-04-20 Various bug fixes and game mode improvements! ### 1.3.4 — 2026-04-10 Even more customization settings - change the date format, change the starting day, and choose your preferred interface. ### 1.3.2 — 2026-04-07 Various bug fixes ### 1.3.1 — 2026-04-02 Bug fixes ## More apps by Maarten Claessen - [Puzzoku](https://appshunter.io/ios/app/puzzoku/id6760819328) - [Hexercise](https://appshunter.io/ios/app/hexercise/id6762805462) - [Shift Go](https://appshunter.io/ios/app/shift-go/id6762990205) All apps by Maarten Claessen: https://appshunter.io/developer/1885901059 ## Related topics [doomsday trainer](https://appshunter.io/ios/topics/doomsday-trainer) · [doomsday method](https://appshunter.io/ios/topics/doomsday-method) · [the doomsday](https://appshunter.io/ios/topics/the-doomsday) --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-30.*