What Day Was I Born?
Pick your date of birth to see the day of the week you were born on. It works for any date from October 15, 1582, when the Gregorian calendar began.
Find the day of the week
Any date from October 15, 1582, when the Gregorian calendar began.
Pick the month, day and year you were born and the weekday appears here.
How the day of the week is worked out
The calculator counts the days from a fixed starting point to your date of birth and divides by seven; the remainder is the weekday. It uses whole calendar dates only, so your time zone cannot shift the answer.
Leap years follow the Gregorian rule: a year divisible by 4 has a February 29, except century years, which need to be divisible by 400. So 2000 was a leap year but 1900 was not, and 2100 will not be.
Worked examples
| Date | Day of the week |
|---|---|
| July 4, 1776 | Thursday |
| January 1, 1900 | Monday |
| March 1, 1900 | Thursday |
| June 6, 1944 | Tuesday |
| January 1, 2000 | Saturday |
| February 29, 2000 | Tuesday |
| September 11, 2001 | Tuesday |
| February 29, 2024 | Thursday |
Each of these was checked by hand with Zeller's congruence, a formula for the weekday of any Gregorian date, as well as by the calculator.
Dates before the Gregorian calendar
The Gregorian calendar replaced the Julian calendar in 1582. In the countries that switched first, Thursday, October 4, 1582 was followed by Friday, October 15, 1582 (Encyclopaedia Britannica). Earlier dates were kept on the Julian calendar everywhere, so the calculator does not accept them.
Britain and its colonies, including the American colonies, switched later. Under the Calendar (New Style) Act 1750, the day after September 2, 1752 was “accounted to be the fourteenth day of September.” The same Act moved the start of the year from March 25 to January 1. The Act received Royal Assent on May 22, 1751 (Old Style), as the Journal of the House of Lords records. For a date up to September 2, 1752, the calculator also shows the weekday the date had if it was written in the old Julian calendar, and the matching Gregorian date. September 3 to 13, 1752 never existed in Britain and its colonies, so for those dates the calculator says so instead. Other countries switched at other times, so for an old record check which calendar it was written in.
More about your birthday
The age calculator gives your exact age in years, months and days. The birthday calculator shows which day of the week your next birthday falls on, and what generation am I names your generation from your birth year.
Sources
- legislation.gov.uk (The National Archives), “Calendar (New Style) Act 1750 (24 Geo. 2 c. 23)”, 24 Geo. 2 c. 23 (1750). Checked November 10, 2026.
- British History Online, “House of Lords Journal Volume 27: 22 May 1751”, records the sitting of May 22, 1751 (Old Style). Checked November 10, 2026.
- Encyclopaedia Britannica, “Ten Days That Vanished: The Switch to the Gregorian Calendar”, no publication date shown. Checked November 10, 2026.
Calendar data version 2026-11-10.