Day of the Week Calculator

Find the day of the week for any date, past or future — including the day you were born.

Date

Gives the day of the week of any date from the year 1000 to 9999 — a birthday, a historical event, a date years ahead — with which of its weekday in the month it is, its week number, the month's calendar and the weekday it falls on in each of the next ten years.

Working it out by hand

John Conway's doomsday method rests on dates that share a weekday within any one year: 4 April, 6 June, 8 August, 10 October and 12 December, 9 May and 5 September, 11 July and 7 November, the last day of February, and 3 January (4 January in a leap year). That weekday is the year's doomsday.

To find it, count weekdays from Sunday as 0. Take the century's anchor day — 1800s Friday, 1900s Wednesday, 2000s Tuesday and 2100s Sunday — then add the year within the century divided by 12, the remainder, and that remainder divided by 4, dropping fractions, and keep the remainder after dividing by 7. From the doomsday nearest the date, count days forward or back.

For 15 August 1947: the 1900s anchor is Wednesday (3). 47 ÷ 12 is 3 remainder 11, and 11 ÷ 4 is 2. 3 + 3 + 11 + 2 = 19, which leaves 5 after dividing by 7: the doomsday of 1947 is a Friday. 8 August is a doomsday, and 15 August is 7 days later, so it is also a Friday.

Examples

1 January 2000

The first day of 2000 was a Saturday, the 1st Saturday of January 2000.

Republic Day, 26 January 1950

The Constitution of India came into force on a Thursday, the 4th and last Thursday of January 1950.

The Moon landing, 20 July 1969

Apollo 11 landed on the Moon on a Sunday (in UTC), the 3rd Sunday of July 1969.

Frequently asked questions

A year of 365 days is 52 weeks and one day, so a date falls one weekday later each year, and two after a 29 February. 15 August is a Saturday in 2026, Sunday in 2027 and Tuesday in 2028.

The Gregorian calendar began on 15 October 1582, a Friday, which followed Thursday 4 October in the Julian calendar: ten dates were skipped, the weekdays were not. Britain and its colonies changed in 1752, going from Wednesday 2 September to Thursday 14 September, and other countries later still. The tool extends the Gregorian calendar backwards, so for a date written in the Julian calendar — as most records before the change are — convert it first, or the weekday will be wrong.