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Week Number of the Year
Determine the week number of the year for any date easily.
How to Use
1
Choose a date or leave it for today.
2
Click "Calculate".
3
View the week number, day, and progress.
Enter Date
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About This Tool
What is the ISO Week Number (ISO 8601)?
An international numbering system that assigns each week a number from 1 to 52 or 53. Week 1 contains the year's first Thursday. The week starts on Monday per ISO standard. Widely used in business, project management, and scheduling.
How is it calculated?
Calculated by finding the nearest Thursday to the given date, then counting days from the start of the year to that Thursday, and dividing by 7. This ensures results match the international ISO 8601 standard.
Practical Uses
- Project management and weekly task planning
- Financial and weekly business reports
- Manufacturing and production schedules
- Academic and school calendars
- International coordination and meeting scheduling
Fact: Most years have 52 weeks, but some have 53. A year has 53 weeks if January 1 falls on Thursday, or if it's a leap year and January 1 falls on Wednesday or Thursday.
Sources & References
Frequently Asked Questions
An international numbering system (ISO 8601) that assigns each week a number from 1 to 52 or 53. Week 1 contains the first Thursday of the year.
Most years have 52 weeks, but some have 53 if January 1 falls on Thursday, or it's a leap year starting on Wednesday or Thursday.
Used in project management, manufacturing schedules, financial reports, academic calendars, and international coordination.
In ISO, the week starts on Monday and Week 1 contains the first Thursday. In the North American system, the week starts on Sunday and Week 1 contains January 1. This means the same date may have a different week number depending on the system.
ISO 8601 is the international standard adopted in most European and Asian countries, used in global corporations, financial reports, computer systems, project management, and manufacturing schedules.
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