Week Number Calculator
Find the ISO 8601 week number for any date, plus the week of the month, day of year, and days remaining. Everything runs in your browser.
Enter a date as YYYY-MM-DD
FAQ
How is the ISO week defined?
Weeks start on Monday and week 1 contains the year's first Thursday, so late December can fall in next year's week 1 and early January in the previous year's week 52/53.
How is week-of-month counted?
The week containing the 1st is week 1, advancing each Monday. Organizations may use different conventions.
Does a year always have 52 weeks?
Mostly 52, but years starting on Thursday (or Wednesday in leap years) have 53 ISO weeks—like 2020 and 2026.
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