Day of the Week Calculator: What Day Was It?
This day of the week calculator tells you which weekday any date falls on, from the year 1 to 9999. Check the day you were born, the weekday of a historical event, or whether a future birthday falls on a weekend. It also shows the day of the year, whether the year is a leap year and the weekday of the same date in the years ahead.
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Quick answer: Pick a date and the tool says which day of the week it was or will be. For example, July 20, 1969 (the Moon landing) was a Sunday, and January 1, 2000 was a Saturday.
How to use the day of the week calculator
- Choose a date with the date picker or type it in. It opens on today.
- Read the weekday in the large text, plus the day of the year and how many days ago or ahead it is.
- Check the table to see which weekday the same date falls on in the coming years. Weekends are in green, handy for planning birthdays and anniversaries.
- Try a preset to see the weekday of a famous date.
How to work out the day of the week in your head
Mathematician John Conway’s Doomsday rule lets you find any weekday with a little practice. Each year has a “doomsday”, a weekday shared by easy-to-remember dates: 4/4, 6/6, 8/8, 10/10, 12/12, 5/9, 9/5, 7/11, 11/7, the last day of February and March 14 (Pi Day). In 2026 the doomsday is Saturday, so October 10, 2026 is a Saturday, and October 14 is four days later, a Wednesday.
The doomsday moves forward one weekday each year, and two after a leap day. The anchor days for each century are Tuesday for the 1900s, Wednesday for the 2000s and Friday for the 2100s.
Leap years
A year is a leap year if it divides by 4, except century years, which must divide by 400. So 2000 and 2024 were leap years, while 1900 and 2100 are not. A date moves forward one weekday each year, or two if February 29 falls in between, which is why your birthday rarely lands on the same weekday two years running.
Calendar notes
The calculator uses the Gregorian calendar, introduced in 1582 and adopted by Britain and its colonies in 1752. For earlier dates, historians often quote the old Julian calendar, which can differ by 10 or more days.
Related tools: the age calculator works out your exact age, days between dates counts the gap between two dates, and the week number tool shows the ISO week for any date.
FAQ
What day of the week was I born?
Enter your birth date and the answer appears at once. The table also shows the weekday of your birthday in the next few years.
How often does Friday the 13th happen?
At least once and at most three times every year. The tool lists the months for the year you pick.
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