time-date Verified Precision Tool
Week Number Calculator
Determine the ISO 8601 week number (1 through 53) and week year for any selected date.
Date Calculation Result
ISO Week 24
ISO Week Year: 1995
Mathematical Formula
ISO Week 1 is the week containing the first Thursday of January
Overview & Explanation
Calculates the official ISO 8601 week number for business and project planning.
How It Works
- Identifies the week containing the first Thursday of the calendar year.
Practical Applications
- Corporate project planning by week number.
- Supply chain week tracking.
Worked Example: Sept 1, 2026
Find ISO week.
1
Calculate ISO Week
Count weeks from first Thursday
= Week 36
Frequently Asked Questions
What is an ISO week number?
An ISO week number is an international standard that numbers weeks from 1 to 52 or 53 starting on Monday.
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