π Week Number Calculator
Find the ISO week number for any date
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Select a date to see the week range
Current Year Week Overview
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What is ISO Week Number?
The ISO week number is a standard way to identify weeks within a year. According to ISO 8601:
- Weeks start on Monday and end on Sunday
- Week 1 is the week containing the first Thursday of the year
- A year can have 52 or 53 weeks
- The last days of December may belong to week 1 of the next year
ISO week numbers are widely used in business, project management, and international scheduling.