What Day of the Week Is It?

How a date’s weekday is worked out

The calculator counts the days between your date and a fixed reference day, then divides by seven. The remainder is the weekday. Because it uses whole-day arithmetic in your browser, it works for every date from year 1 to 9999 and gives the same answer in every time zone.

Why a date moves one weekday each year

A common year has 365 days, which is 52 weeks plus one day. So a date that is a Saturday this year is a Sunday next year: 31 October 2026 is a Saturday and 31 October 2027 a Sunday. When 29 February falls in between, the date jumps two days. That is why your birthday drifts through the week and returns to the same weekday after 5, 6 or 11 years. The Gregorian calendar repeats exactly every 400 years, because 400 years contain 146,097 days, exactly 20,871 weeks.

The Doomsday method

You can find any weekday in your head with the mathematician John Conway’s Doomsday rule. In every year, 4/4, 6/6, 8/8, 10/10 and 12/12 fall on the same weekday, called the doomsday, as do 9/5, 5/9, 7/11, 11/7, 14 March and the last day of February. In 2026 they are all Saturdays. Find the nearest of these dates and count forward or back. Open Work it out in your head above to see each step for the date you picked.

Old dates and the Julian calendar

Before 15 October 1582 the Julian calendar was in use, and many countries switched much later: Britain and its colonies in 1752, Russia in 1918, Greece in 1923. The weekday cycle never broke, only the date numbers jumped: in Britain, Wednesday 2 September 1752 was followed by Thursday 14 September. For such dates you can switch the calculator to Julian, and it also shows the matching Gregorian date. The Battle of Hastings, 14 October 1066, was a Saturday.

To count the days between two dates use the days between dates calculator, and to see how long is left until a date use the countdown. Nothing you enter here is sent anywhere.