Doomsday Method vs Grammar Jammer
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Doomsday Method
Master the art of calculating weekdays for any date with this comprehensive educational app. Learn a proven technique, practice with interactive exercises, and track your progress to sharpen your mental arithmetic skills.
- Learn Doomsday Method principles
- Interactive examples and tips
- Dedicated training mode
- Progress tracking and statistics
- User-friendly interface
Read full descriptionHide full description
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/
Grammar Jammer
Learn English tenses with visual grammar formulas. This app presents active and passive voice tenses with affirmative, negative, and interrogative structures. Includes tests and exercises for mastery.
- Visual grammar formulas
- 16 active voice tenses
- 10 passive voice tenses
- Affirmative, negative, interrogative structures
- Tests and exercises
Read full descriptionHide full description
This app has been created to help students with forming English tenses correctly using grammar formulas. The app visually presents 16 active voice tenses and 10 passive voice tenses. Each tense show affirmative, negative, and interrogative structures. There are tests and extra exercises to help you master all English tenses.
Screenshots
Verdict
The clearest difference is price: Doomsday Method at Free against Grammar Jammer's $3.99. Doomsday Method also leads on ratings volume (3 vs 1). Grammar Jammer's advantage is rating (5.0 vs 4.7). On review sentiment, update cadence, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Doomsday Method is free to download; Grammar Jammer costs $3.99 up front. Doomsday Method sells 1 one-off in-app purchase and Grammar Jammer sells 2 one-off in-app purchases. Whichever you choose, the download price is not the number that matters.
Grammar Jammer holds the better App Store score, 5.0 against 4.7. Both are backed by a comparable volume of ratings — 3 and 1 respectively. Written reviews split almost evenly too, at 100% and 100% positive.
Both ship on a similar rhythm, roughly monthly. The most recent releases landed on October 25, 2026 and October 19, 2026 respectively.
| Parameter | Doomsday Method | Grammar Jammer |
|---|---|---|
| Price | Free — better | $3.99 |
| Rating | 4.7 (3 ratings) | 5.0 (1 ratings) — better |
| Positive reviews | 100.0% of reviews | 100.0% of reviews |
| Number of ratings | 3 — better | 1 |
| Update frequency | Monthly | Monthly |
| Ads | No | No |
| In-app purchases | Yes | Yes |
| Monetization | Free — better | Paid |
| Devices | iPhone | iPhone |
| Requires iOS | 17.0 — better | 18.1 |
| Further details — not scored | ||
| Size | 10 MB | 1 MB |
| Age rating | 4+ | 4+ |
| Developer | Leon Grimmeisen | VITALY KIRILOV |
Customer experience
Doomsday Method
Grammar Jammer
In-app purchases
Doomsday Method
- Doomsday Pro$9.99
Grammar Jammer
- Extras$3.99
- Premium Lifetime Access$3.99
Questions
Is Doomsday Method free?
Is Grammar Jammer free?
Which has better reviews, Doomsday Method or Grammar Jammer?
Do Doomsday Method or Grammar Jammer have ads?
Which is updated more often, Doomsday Method or Grammar Jammer?
Other comparisons















