What Day of the Week Was I Born? Find the Weekday for Any Date

To find what day of the week you were born, enter your birth date in a day-of-the-week calculator, or work it out by hand with the Doomsday method in under a minute. For example, July 20, 1990 was a Friday, and today, October 2, 2026, is a Friday too.

The quickest route is our day of the week calculator, which works for any date. If you’d like to do it in your head, or check a spreadsheet, this guide teaches the Doomsday method step by step, works through five examples, and shows the Excel formulas that return a weekday name. It also covers two traps: leap years and dates from before the Gregorian calendar.

The idea behind the Doomsday method

The method was devised by the mathematician John Horton Conway, who also invented the Game of Life; the NIST Dictionary of Algorithms and Data Structures describes it as simple enough to memorize and do mentally. It rests on one fact: in any year, a set of easy-to-remember dates all fall on the same weekday, called that year’s “doomsday”. In 2026, every one of these dates is a Saturday:

• 4/4, 6/6, 8/8, 10/10 and 12/12 (April 4, June 6, August 8, October 10, December 12)
• 5/9 and 9/5, 7/11 and 11/7 (May 9, September 5, July 11, November 7)
• March 14 (Pi Day) and the last day of February
• January 3 in a common year, or January 4 in a leap year

If you know the doomsday for a year, you can reach any date by counting from the nearest of these anchors. The work is finding the doomsday.

Step by step: what day of the week was I born?

1. Start with the century’s anchor day. 1800s: Friday. 1900s: Wednesday. 2000s: Tuesday. 2100s: Sunday.
2. Take the last two digits of the year and divide by 12. Note the whole number (a) and the remainder (b).
3. Divide the remainder b by 4, ignoring any fraction. Call that c.
4. Add a + b + c and move that many days forward from the century’s anchor day (you can subtract 7s first to keep it small). That’s the year’s doomsday.
5. Find the nearest doomsday date in your birth month from the list above and count forward or back to your birthday.

It helps to number the days: Sunday 0, Monday 1, Tuesday 2, Wednesday 3, Thursday 4, Friday 5, Saturday 6. Then you can add the numbers and take the remainder after dividing by 7.

Worked examples

Take July 20, 1990 slowly. The century anchor for the 1900s is Wednesday. 90 ÷ 12 is 7 remainder 6, so a = 7 and b = 6. 6 ÷ 4 is 1 (ignoring the fraction), so c = 1. The total is 14, which is exactly two weeks, so the 1990 doomsday is Wednesday again. July 11, 1990 was therefore a Wednesday, and July 20, nine days later, was a Friday.

Every answer in the table matches our calculator. You can check a birthday in any year from its own page too, such as what day July 20 falls on.

Leap years: the January and February trap

The only part of the anchor list that changes is the start of the year. In a leap year, the doomsday dates for January and February are January 4 and February 29 instead of January 3 and February 28. It’s the easiest step to forget, and forgetting it puts January and February dates out by one day.

Example: January 1, 2000. The 2000 doomsday is Tuesday (the last two digits are 00, so there is nothing to add). 2000 was a leap year, so the January anchor is January 4, a Tuesday. January 1 is three days earlier: a Saturday. If you’d used January 3, you’d have got Sunday. Our leap year guide explains why 2000 was a leap year but 1900 wasn’t.

Dates before the Gregorian calendar

The method assumes the Gregorian calendar throughout. That calendar began in 1582, when October 4 was followed by October 15, but Britain and its American colonies didn’t adopt it until 1752, when September 2 was followed by September 14. A date written in an English or colonial record before September 1752 is a Julian calendar date, so its weekday won’t match a Gregorian calculation. For birthdays this is never a problem; for genealogy it can be.

Finding the weekday in Excel

With the date in A1, these formulas return the weekday. Microsoft documents the format codes in its guide to formatting dates and the numbering on the WEEKDAY function page.

• =TEXT(A1,"dddd") returns the full name, such as Friday. Use "ddd" for the short form, Fri.
• =WEEKDAY(A1) returns a number from 1 (Sunday) to 7 (Saturday). =WEEKDAY(DATE(1990,7,20)) returns 6.
• =WEEKDAY(A1,2) numbers Monday as 1 through Sunday as 7, so the same date returns 5.

One caveat: Excel treats 1900 as a leap year for compatibility with Lotus 1-2-3, so Microsoft notes that WEEKDAY gives wrong results for dates before March 1, 1900.

What else you can work out from a birth date

Once you have the weekday, the same date answers other questions. Someone born on Friday, July 20, 1990 is 36 years, 2 months and 12 days old on October 2, 2026, which is 13,223 days. The age calculator shows your exact age, the weekday you were born and how long until your next birthday, and the date duration calculator counts the days between any two dates.

Frequently asked questions

What day of the week was I born?

Enter your birth date in the day of the week calculator for an instant answer, or use the Doomsday method above: find the year’s doomsday from the century anchor, then count from the nearest anchor date in your birth month.

What day of the week is it today?

Friday, October 2, 2026. It’s day 275 of the year and in ISO week 40.

What day of the week was January 1, 2000?

Saturday. 2000 was a leap year, so its January anchor date is January 4, a Tuesday, and January 1 is three days before.

Do days of the week repeat every year?

Not quite. A date moves one weekday later each year, or two after February 29. The whole calendar repeats exactly only every 400 years, though many individual years share a calendar.

What day of the week was July 20, 1969?

Sunday. The 1969 doomsday was a Friday, so July 11 was a Friday and July 20, nine days later, was a Sunday.