📚 Trivia Collection
Every tool on this site comes with a "Side Note" section — trivia or background knowledge beyond the calculator itself. Follow your curiosity from topic to topic, Wikipedia-style.
Crypto
- Side Note — The Most-Hacked Passwords in the World
- Side Note — The Inventor of MD5 and the Trajectory of a "Broken" Algorithm
- Side Note — SHAttered: A Collision Attack 9.2 Quintillion Operations in the Making
- Side Note — Bitcoin Mining and the Astronomical Scale of SHA-256 Computation
- Side Note — Why "512 Bits"? Bit Length and the Meaning of Security
- Side Note — The Birth of Keccak and the NIST Competition: Five Years to Crown the Next Standard
- Side Note — The Battle of Passwords and Hashes: Why BCrypt Is Chosen
- Side Note — Behind Authentication: What Those Few Hundred Milliseconds on Login Are
Developer Tools
- Side Note — The Surprising History of CSV: 40 Years Without a Standard
- Side Note — The Origin of JSON: "Discovered", Not Invented
- Side Note — 50 Years of SQL: A History of Relational Databases
- Side Note — The 80-Character Curse: A Tradition from Punch Cards
- Side Note — Why JSON Won Over XML
- Side Note — Base64, Email, and the URL Collision
- Side Note — Why Excel Corrupts CSV Files
- Side Note — Why ASCII is 7-Bit
- Side Note — The Birth of robots.txt: The Day the Internet Got Manners
- Side Note — The Luhn Algorithm — The Guardian of Card Numbers Since 1954
- Side Note — Where "Valid" Ends and "Corrupt" Begins
- Side Note — Why Basic Auth survives despite its age
Math
- Side Note — History of the Calculator: From a 30-Ton Monster to the Smartphone
- Note — Is Compound Interest "Humanity's Greatest Invention"?
- Note — Japan's Consumption Tax History: 35 Years of Change
- Note — The Limits of BMI and the "Overweight Paradox"
- Note — The Illusion That "One Free" Beats "Half Price"
- Side Note — Why the 4-digit vs 3-digit gap exists
- Side Note — Why a Linear Function Is Called "Linear"
- Side Note — The Origin of the Word "Parabola"
- Side Note — The Rivalry Behind the Cubic Formula
- Side Note — Why do experts dislike pie charts?
- Side Note — Ellipses in planetary orbits
- Side Note — Hyperbolas and navigation
- Side Note — Compound interest and the number e
- Side Note — Logarithms in decibels and earthquake magnitude
- Side Note — Gauss and the legend of 1 to 100
- Side Note — Geometric growth and the paper-folding myth
- Side Note — Fibonacci, the golden ratio, and Binet's formula
- Side Note — Why prime numbers matter
- Side Note — RSA encryption and the hardness of factorization
Date/Time
- Side Note — Ways of Counting Age Around the World
- Side Note — The Surprising Origin of Yakudoshi
- Side Note — The History of Japan's Era Name System
- Side Note — Humanity's Quest for Precision — Atomic Clocks and Leap Seconds
- Side Note — World Speed Records — Various Speeds Measured with a Stopwatch
- Side Note — The Pomodoro Technique and the Story Behind Its 25-Minute Interval
- Side Note — The World's Unusual Timezones — Countries with 30- and 45-Minute Offsets
- Side Note — How the World Agreed on Time
- Side Note — Japan's Public Holidays vs. the World — Many Holidays, Few Paid Vacations Taken
- Side Note — The Mystery of Rokuyou — No Scientific Basis, Yet 60–70% Consult It
- Side Note — History of Japanese Era Names — A 1,400-Year Tradition Unique to Japan
- Side Note — Why April 1 Birthdays Are One Year Ahead
Network
- Side Note — The Birth of REST: How Roy Fielding's Dissertation Changed Web Development
- Side Note — The Birth of the URL: Tim Berners-Lee and the Dawn of the World Wide Web
- Side Note — The IPv4 Exhaustion Problem: The Day 4.3 Billion Addresses Ran Out
- Side Note — IP Address Trivia: 8.8.8.8 and the End of IPv4
- Side Note — WHOIS history and the GDPR turning point
- Side Note — The History of Domain Names and the Birth of WHOIS
Money
- Side Note — What's the hourly rate for a ¥10M annual salary?
- Side Note — Why "percent" and "percentage points" are different
- Side Note — Why Is It Called "Hometown Tax"?
- Side Note — Hyperinflation and the History of Money
- Side Note — The Rule of 72 and the Mystery of Compound Interest
- Side Note — Why take-home pay in Japan is typically 75–85% of gross
- Side Note — The Mystery of the "35-Year" Home Loan
- Side Note — Why Compound Interest Was Called "the Eighth Wonder of the World"