What day of the week is it?

What day of the week was I born?

Enter your birth date — the calculator shows the weekday, and the table lists which weekday your birthday falls on in the years around it.

What day of the week was July 4, 1776?

A Thursday, in the Gregorian calendar the colonies were already using. January 1, 2000 was a Saturday.

Why does my birthday move one day each year?

A year of 365 days is 52 weeks and 1 day, so a date moves forward one weekday each year — and two days when February 29 falls in between.

How far back does it work?

Any date from year 1 onward, counted in the Gregorian calendar — the one used today. Dates before a country switched from the Julian calendar (1752 in Britain and its colonies) were written differently back then.

Can I work out the weekday in my head?

Yes, with the Doomsday rule: in any year, 4/4, 6/6, 8/8, 10/10, 12/12 and the last day of February fall on the same weekday. In 2026 that is a Saturday, so June 6 and December 12 are Saturdays.

Does the weekday pattern ever repeat exactly?

Yes, every 400 years. The 400-year Gregorian cycle contains 146,097 days, which is exactly 20,871 weeks, so a date falls on the same weekday as the same date 400 years earlier or later. That is why the calendar of 2026 will look like that of 2426.

What day of the week was a date before 1582?

The calculator gives the weekday as if the Gregorian rules had always applied. Historical records may disagree: the Julian calendar was used in Europe until the Gregorian reform of 1582 (and much later in some countries), so a document dated in the old style can fall a number of days away from the same date in the Gregorian count.

How the weekday is computed

The calculator counts the days from a fixed reference date, 1 January 1970, which was a Thursday, and takes that count modulo 7. For Saturday, January 1, 2000, the count is 10957 days after the reference; 10957 leaves a remainder of 2 when divided by 7, and that many steps forward from Thursday lands on Saturday. The day count itself relies on the Gregorian leap-year rule: every year divisible by 4 is a leap year, except century years not divisible by 400.

Worked example: a birthday through the years

February 14 falls on Saturday in 2026, Sunday in 2027 and Monday in 2028. A common year of 365 days is 52 weeks plus 1 day, so the weekday moves forward by one; it then moves by two across a leap year's February 29, so 2029 brings Wednesday. For dates before 1970 the same count simply runs backward: Thursday, July 4, 1776 comes out as a Thursday.

The Doomsday shortcut

John Conway's Doomsday rule says that 4/4, 6/6, 8/8, 10/10 and 12/12 fall on the same weekday in any year, the year's doomsday. In 2026 that is Saturday, in 2027 Sunday and in 2028 Tuesday. Knowing the doomsday, you count forward or back from the nearest of those dates. For the last day of February the same weekday applies, which is the 28th in common years and the 29th in leap years.

Common mistakes

Mixing day and month in an international date (4/7 is April 7 in the US and July 4 in most of the world) gives a different weekday, so check the format. Counting weekdays from the wrong anchor year is another; the doomsday changes every year. And remember the date a document gives may be in the Julian calendar if it comes from before your country's changeover.

Sources: the Gregorian leap-year rule and the length of the 400-year cycle — U.S. Naval Observatory, “Calendar Information”; the Doomsday rule — J. H. Conway, “Tomorrow Is the Day After Doomsday” (Eureka, 1973). Related: date calculator, day of the year calculator, leap year calculator and age calculator.