Week Number Calculator

Calculate the ISO 8601 week number (1-53) for any given date.

Inputs
Results
ISO Week Number
30

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Formula

ISO 8601 week numbering (weeks start Monday, week 1 contains the first Thursday of the year)

Learn How This Works

Time Zone Differences and ISO Week Numbers Explained

How UTC offset math calculates time zone differences, and how the ISO 8601 week-numbering system actually works.

Frequently Asked Questions

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