Week Number Calculator
Calculate ISO 8601 week numbers for any date. Perfect for business planning, project management, and international scheduling with standardized week numbering.
Find Week Number
About ISO 8601 Week Numbers
- • ISO 8601 Standard: International standard for week numbering
- • Week 1: First week containing at least 4 days of the new year
- • Monday Start: Weeks always start on Monday and end on Sunday
- • Year Overlap: Week 1 may start in December of the previous year
- • Example: Week 1 of 2025 starts on December 30, 2024 (Monday)
- • Business Use: Widely used in Europe and business planning
- • 53 Weeks: Some years have 53 weeks instead of 52
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