# OtterDay: Calendar Logic Game — Name Any Weekday in 5 Seconds > Learn to mentally calculate the day of the week for any date. (iPhone/iPad app by FELIX MANUEL PLAGGE.) - Source: https://appshunter.io/ios/app/otterday-calendar-logic-game/id6747994124 (this page in markdown: same URL + `.md`) - Developer: [FELIX MANUEL PLAGGE](https://appshunter.io/developer/1823761397) - Category: Games, Education, Puzzle, Trivia - Price: Free with in-app purchases - Rating: 5.00/5 from 1 App Store ratings - Age rating: 4+ - Requires: iOS 15.6 · 162 MB - Languages: American English, French (France), German (Germany), European Portuguese, European Spanish - Released: 2025-08-12 - Data updated: 2026-08-29 - Monetization: free with in-app purchases - User reviews in markdown: https://appshunter.io/ios/app/otterday-calendar-logic-game/id6747994124/reviews.md ## What is OtterDay? CAN YOU NAME THE WEEKDAY OF ANY DATE? OtterDay turns calendar calculation into a fast, satisfying logic game. Just as location-guessing games make geography feel playable, OtterDay does the same for dates. Learn a reliable mental method, practice it step by step, and work toward finding the weekday in five seconds—without checking a calendar. A SMART WORKOUT FOR YOUR BRAIN Every round challenges your logic, memory, number sense, and mental math. Short sessions keep your mind active while you build a practical skill that feels like a superpower: becoming a human calendar. LEARN, PRACTICE, MASTER Futuristic otter guides teach you the method one piece at a time. Start with recent dates, unlock wider ranges across centuries, and train until the calculation becomes second nature. WHY YOU'LL KEEP PLAYING • Guided lessons that explain the calendar method • Written and spoken-date challenges • Speed and precision training • Progress tracking and personal statistics • Achievements for accuracy, endurance, and fast answers • Flexible difficulty for quick practice or serious mastery MADE FOR CURIOUS MINDS OtterDay is designed for people who enjoy Sudoku, logic puzzles, mental math, number games, brain training, and learning clever systems. The method is related to John Conway's Doomsday Algorithm, presented as a focused puzzle adventure rather than a dry lesson. Keep your mind active. Sharpen your logic. Master the calendar—and see how close you can get to five seconds. ## Key features - Interactive otter guides - Learn the date trick step-by-step - Two game modes: written and spoken dates - Achievements for speed and precision - Progress tracking for streaks and times - Works for dates from 1750 to the far future ## Pricing and in-app purchases Base price: Free. **One-time purchases** | Purchase | Price | Type | | --- | --- | --- | | Pro | $6.99 | one-time | | Core | $5.99 | one-time | | Core To Pro | $5.99 | one-time | ## Frequently asked questions about OtterDay ### What is OtterDay? OtterDay is a game that teaches you to calculate the day of the week for any date mentally. It combines brain training with a puzzle adventure featuring otter guides. ### How does OtterDay teach the date trick? OtterDay uses interactive otter guides to teach the 'date trick' step-by-step. You can practice with written dates or spoken challenges in two distinct game modes. ### Can OtterDay calculate days for past and future dates? Yes, OtterDay offers a timeless challenge that works for any dates from 1750, covering both past historical dates and dates far into the future. ### What kind of progress tracking does OtterDay offer? OtterDay provides progress tracking so you can see your streaks, best times, and overall brainpower growth. You can also collect rewards for speed, endurance, and precision through achievements. ### What is the age rating for OtterDay? OtterDay has an age rating of 4+, making it suitable for a wide range of users interested in learning and brain training. ### Does OtterDay have ads? Yes, OtterDay contains advertisements. It is a free app with in-app purchases available. ### What devices does OtterDay support? OtterDay is currently supported on iPhone and iPod devices, allowing users on these platforms to learn the date trick. ### How often is OtterDay updated? OtterDay was last updated on June 19, 2026, with version 1.1.7. This indicates a commitment to ongoing development and improvements. ## Version history (last 5 releases) ### 1.2.4 — 2026-08-20 Various improvements to make your experience better! ### 1.2.3 — 2026-08-11 Just a few tweaks to make your experience better! ### 1.2.2 — 2026-08-05 New Hands-Free Mode: Hear the date and answer with the weekday using your voice! (PRO) ### 1.2.1 — 2026-07-18 This version includes several bug fixes. ### 1.2.0 — 2026-07-16 The statistics page just landed, along with a sleek new design! ## Apps similar to OtterDay | App | Rating | Price | Category | | --- | --- | --- | --- | | [WordFlux: Word Puzzles](https://appshunter.io/ios/app/wordflux-word-puzzles/id6757514622) | 5.0 (2) | Free | Games | | [Crystal Abyss](https://appshunter.io/ios/app/crystal-abyss/id6751184987) | — | Free | Games | | [Cosmic Merge](https://appshunter.io/ios/app/cosmic-merge/id6471924647) | 4.4 (5) | Free | Games | | [Tile Tale - a Minimalism Game](https://appshunter.io/ios/app/tile-tale-a-minimalism-game/id577675173) | 4.9 (13) | Free | Games | | [Flags and Capitals 2023](https://appshunter.io/ios/app/flags-and-capitals-2023/id6444810482) | 5.0 (1) | Free | Games | | [GATO APP](https://appshunter.io/ios/app/gato-app/id6444835134) | 5.0 (9) | Free | Games | --- *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 2026-08-29.*