Day of the Week Calculator
Free day of the week calculator: find what day of the week any date falls on, with the day of the year, the week number and how far it is from today.
What it does
This calculator tells you the day of the week of any date in the Gregorian calendar, past or future, together with its day number in the year, how many days are left until the end of the year, its ISO week number and how many days separate it from today. It is useful for birthdays, historical dates, deadlines and planning events.
How to use it
- Choose a date (today is filled in).
- See the day of the week and the full date.
- Check the day of the year, the days left, the week number and the distance from today.
The arithmetic runs in your browser. Nothing you type is sent anywhere and nothing is stored, so you can use these with real numbers.
Frequently asked questions
How can I work out the day of the week in my head?
With Conway's doomsday rule: in every year the dates 4/4, 6/6, 8/8, 10/10, 12/12, 5/9, 9/5, 7/11 and 11/7 fall on the same day of the week. In 2026 that day is a Saturday, so 10/10/2026 is a Saturday.
Does it work for old dates?
It uses the Gregorian calendar for all dates. Most Catholic countries adopted it in October 1582, but Britain and its colonies only in 1752 and Russia in 1918, so older local dates may follow the Julian calendar.
Which years are leap years?
Years divisible by 4, except century years that are not divisible by 400. So 2024 and 2000 were leap years, but 1900 and 2100 are not.
Why does my birthday fall on a different day every year?
Because 365 days are 52 weeks and one day: each year a date moves one day of the week forward, or two after February 29. The same pattern repeats every 28 years in most cases.
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