Doomsday Practice
Learn the Doomsday Algorithm
Only for iPhone
Free · Designed for iPhone. Not verified for macOS.
iPhone
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.
Ratings & Reviews
The developer, Taiyo Tsuchiya, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Taiyo Tsuchiya
- Size
- 855 KB
- Category
- Education
- Compatibility
Requires iOS 26.0 or later.
- iPhone
Requires iOS 26.0 or later. - Mac
Requires macOS 26.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 26.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Copyright
- © 2026 Taiyo Tsuchiya