OmniCalcsWhat Day of the Week Were You Born?
Every date has a weekday — here's how to find yours.
January 1, 2000 was a Saturday. March 15, 1994 was a Tuesday. The weekday of any date is fully deterministic — you just need to count the days and know your starting anchor.
The 400-Year Cycle
The Gregorian calendar repeats exactly every 400 years (146,097 days, which is divisible by 7). That's why the 1600s, 2000s and 2400s share identical calendars — a fact mathematicians love and that makes calendar math tractable by hand.
Why Leap Years Shift Things
A normal year has 365 days = 52 weeks + 1 day, so each year's weekday moves forward by one. A leap year (366 days) adds an extra day and moves it by two. The rule: years divisible by 4 are leap, except centuries not divisible by 400 — so 1900 was not a leap year, but 2000 was.
Try It Yourself
The cleanest manual method is Zeller's congruence, a formula that converts a date into a weekday number without counting each day. It looks intimidating, but it's a short calculation that works for any date in the Gregorian calendar.
Skip the arithmetic — punch a date into our Weekday Calculator to get the day of the week instantly, find how many days until your next birthday with the Days Until Date Calculator, or see how old you are in years, months and days with the Age Calculator.