Day of the Week Calculator

What day of the week were you born

This is the question most people are really asking. Put your date of birth in the field above and the answer is the first thing on the page.

The result also gives you the two things that usually come next. How many days ago it was, which is a larger number than most people expect. And the years your birthday falls on that same weekday again, which is worth knowing if you have ever wanted a birthday on a Saturday.

That second one is not a fixed cycle, whatever you may have read. A date moves forward one weekday each year, and two whenever a leap day falls in between, so the gaps come out uneven. The tool works out the actual years rather than assuming a pattern.

Dates before the calendar changed

Weekday arithmetic quietly breaks on old dates, and almost every calculator gets this wrong.

Most of Europe used the Julian calendar until 1582, and many countries kept it far longer. Britain and its colonies switched in 1752, Russia not until 1918. Each switch skipped days: in Britain, Wednesday 2 September 1752 was followed by Thursday 14 September 1752.

Notice what did not change. The days of the week ran straight on, Wednesday to Thursday, with no gap. The weekday belongs to the day itself, not to the number written on it. So a date recorded before a country's switch is a Julian date, and to get its weekday you first work out which Gregorian date it actually was.

Enter a date before 1923 and this tool says so, gives you both readings, and lets you choose which one you meant. A calculator that silently assumes Gregorian will tell you 2 September 1752 was a Saturday. It was a Wednesday.

Work it out in your head

The doomsday rule turns any date into a few seconds of mental arithmetic, and it is genuinely learnable in an afternoon.

Every year has a doomsday: a single weekday shared by a set of dates that are easy to remember. 4/4, 6/6, 8/8, 10/10 and 12/12 are all the doomsday. So are 5/9, 9/5, 7/11 and 11/7, which pair up as "working nine to five at the seven eleven". So is the last day of February, whether that is the 28th or the 29th.

The doomsday for 2026 is Saturday. Once you know it, take the nearest anchor date to the one you want, count the days between them, divide by seven and keep the remainder. Count that many weekdays on from the doomsday and you have your answer.

Open "work it out in your head" under the result and the tool shows the working for whatever date you have entered, using the real anchor and the real step, so you can check yourself against it while you learn.

Why the calendar repeats

The Gregorian calendar repeats exactly every 400 years. That cycle holds 146,097 days, and 146,097 divides by seven exactly, so the whole pattern of weekdays comes back round.

This is why a future weekday is as certain as a past one, and why calendars from certain earlier years can be reused unchanged. It is also the reason the average Gregorian year is 365.2425 days rather than a rounder number.