Week Number Calculator - What Week Is It? ISO 8601
Calculate the week number for any date using the ISO 8601 week numbering system. Find out what week of the year it is. Supports Shamsi, Gregorian, and Islamic calendars. Perfect for project planning, scheduling, and international date standards.
Enter Date
Current Week Information
Current Week Number
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Current Week Year
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Today's Date
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About Week Number Calculator
Our week number calculator uses the ISO 8601 standard, which is the international standard for week numbering. This system defines weeks as starting on Monday and assigns week numbers from 1 to 52 or 53, depending on the year.
ISO 8601 Week Numbering Rules:
- Weeks start on Monday and end on Sunday
- Week 1 is the first week with a Thursday in the year
- If January 1st falls on a Friday, Saturday, or Sunday, it belongs to the last week of the previous year
- A year can have 52 or 53 weeks depending on how the days align
- The week year may differ from the calendar year for dates in early January or late December
Use Cases:
- Project planning and scheduling
- Business reporting and analytics
- Academic calendar planning
- Event scheduling and coordination