Day of the Week Calculator
Find out what day of the week any date falls on — past or future — plus the day of the year, the ISO week number, whether it's a leap year, and how many days it is from today. Runs in your browser.
FAQ
How do I find what day of the week a date was?
Enter the date and the tool shows the weekday instantly — 1 January 2000 was a Saturday. It works for past and future dates and also gives the day-of-year and ISO week number.
What is an ISO week number?
The ISO 8601 week number runs 1-53, where week 1 contains the first Thursday of the year and weeks start on Monday. It's widely used in business and scheduling.
How do I know if a year is a leap year?
Divisible by 4, except century years which must also be divisible by 400 — so 2000 was a leap year but 1900 was not. The tool flags it for your date.
Is the calculation private?
Yes — it runs entirely in your browser; nothing is sent or stored.
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