Week Number Finder
Check the current ISO week number, dates, and total weeks for any given year.
About Calculator
The Week Number Finder instantly displays the ISO 8601 week number for any date you select. It also shows the first and last day of that week and the total number of weeks in the given year.
ISO week numbering is the international standard for date-based reporting. Week 1 is the week containing the year's first Thursday. This system is widely used in logistics, supply chain, accounting periods, and sprint planning.
Frequently Asked Questions (FAQ)
Why does the ISO week number sometimes differ from what I expect?
ISO 8601 defines week 1 as the week with the first Thursday of the year. This means Jan 1 can fall in week 52 or 53 of the previous year.
Can a year have 53 weeks?
Yes. Years that start on Thursday (or leap years starting on Wednesday) have 53 ISO weeks.
What day does an ISO week start on?
ISO weeks always start on Monday and end on Sunday.
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