Modulo Calculator. vs Doomsday Trainer

The Modulo Calculator app lets you calculate the modulo of two numbers. Modulo operation is the remainder after division of one number by another. This is often needed by programmers and computer scientists. • Short form of Modulo operation is mod and the symbol is %. • Support for exponential notation (^ power) • Support for calculations including: inverse (^-1), addition, subtraction, multiplication and division • Support for decimal numbers • See how the modulo operation result differs between different modulo definitions used by programming languages • Supported modulo definitions: Euclidean Modulo, Truncated Modulo and Floored Modulo • See how many times the second number fits in the first one • Lets you copy the result to your clipboard • Light and dark mode

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.