Sieve of Fortune — Your Daily Lucky Number

A real daily lucky number from Ulam's 1956 sieve — shaped by date, season, time and place, with the full reasoning shown.

Every day has a lucky number. Sieve of Fortune finds yours — and shows its work. Most lucky-number apps invent a number out of thin air. This one draws it from genuine mathematics: the lucky-number sieve defined in 1956 by Gardiner, Lazarus, Metropolis and Ulam. Their sieve strikes out numbers by position rather than value, and what survives — 1, 3, 7, 9, 13, 15, 21, 25, 31… — behaves eerily like the primes. Your daily number is always one of these true survivors. HOW YOUR NUMBER IS CHOSEN Six facts about the present moment, each weighted by a lucky number, add up to one position in the sequence: • The day of the year, weighted by 7 • The digit sum of the year, weighted by 13 • The season, weighted by 31 (a lucky prime) • The quarter of the day — morning, afternoon, evening or night — weighted by 3 • Your place on Earth, taken from your timezone name • Optionally, the letters of your name The popup prints this arithmetic as a ledger, ending in the modular step that lands on your number. Nothing is hidden and nothing is random: the same person in the same place gets the same number, until the hour turns or the day changes. Add your name, and your number quietly diverges from everyone else in your city. WATCH THE SIEVE WORK Every time you open the popup, an animated grid of the numbers 1–63 replays the sieve pass by pass — "next survivor is 7, strike every 7th remaining number" — until only the lucky ones remain, glowing, with yours picked out in gold. It is the definition of a lucky number as something you watch rather than read. LEARN SOMETHING EVERY DAY • A rotating number-theory fact each day: twin luckies, the Goldbach analogue, lucky primes, why 13 is mathematically lucky after all • Badges when your number is a lucky prime or a palindrome • Your number shown among its neighbours in the sequence • A link to the mathematics for the curious PRIVATE BY CONSTRUCTION • Zero permissions requested — no tabs, no browsing history, no location access • Everything is computed locally in the popup; there is no server, no account, no analytics • The "place" factor is simply your system timezone name, folded into one small number • If you add your name, it is stored only in the extension's own local storage on your device A small, honest, daily ritual: one number, its reasons, and a little more number theory than you had yesterday. Lucky numbers are sequence A000959 in the On-Line Encyclopedia of Integer Sequences.