Day of the week calculator
What day of the week any date falls on, past or future.
About this calculator
What day of the week was I born? This day of the week calculator tells you the weekday for any date, past or future.
It also shows the day of the year, the ISO week number, the quarter, whether it's a leap year and how many days away the date is.
How it works
Uses the calendar we use today, the Gregorian calendar, for every date. Week numbers follow the ISO standard, where week 1 is the week with the year’s first Thursday.
Last reviewed:
Common questions
What day of the week was I born?
Enter your date of birth to see it. It's a favourite question for birthdays and anniversaries.
What is an ISO week number?
A standard way of numbering the weeks of a year, used widely in Europe and in business. Weeks start on Monday, and week 1 is the one containing the first Thursday of the year.
How do I know if a year is a leap year?
It's divisible by 4, except century years, which must be divisible by 400. So 2000 was a leap year but 1900 was not.
The story behind it
Where the idea came from: The Gregorian calendar we use today was introduced by Pope Gregory XIII in 1582 to fix the drift of the older Julian calendar.
When the new calendar began, ten days were skipped: Thursday 4 October 1582 was followed by Friday 15 October. The days of the week kept their order, which is why weekdays can be worked out across the centuries. Some countries switched much later, Britain in 1752.
Why you can trust this calculator
- It runs in your browser. Nothing you type into it is sent anywhere.
- The method is explained on this page, so you can check it yourself.
- Free to use, with no sign-up.
- Results are estimates, so please double-check anything important.
- Spotted a mistake? Tell us and we'll look into it.
After 15 years as a mathematics educator, I built CalculStore to give students, teachers, professionals and anyone working with numbers simple, reliable tools.
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