Day of the Week Calculator
Find the weekday for any date, with its ISO weekday number and day of the year.
How to use it
- Pick a date Any past or future date.
- See the weekday The day name appears instantly.
- Check the extras ISO weekday number and day of the year too.
Examples
| 8 Jan 2024 | Monday |
|---|---|
| ISO weekday | 1 |
About this tool
Need to know which day of the week a date lands on — for a birthday, a deadline or a historical event? Enter any date and this calculator names the weekday at once.
It also gives the ISO weekday number, where Monday is 1 and Sunday is 7, and the day of the year, both handy for spreadsheets and scheduling. The weekday name follows the page’s language, and the whole calculation runs in your browser.
Frequently asked questions
Does it work for historical dates?
Yes, using the proleptic Gregorian calendar, so it's consistent for dates far in the past or future.
What is the ISO weekday number?
Under ISO 8601, Monday is 1 and Sunday is 7, which is common in spreadsheets and programming.
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Updated June 13, 2026