Week of the Year Calculator (ISO 8601 Week)

Determine the standard ISO 8601 week number (W01 through W53) and ISO week-numbering year for any date.

How It Works & Processing Standards

Determine the standard ISO 8601 week number (W01 through W53) and ISO week-numbering year for any date.

Your input data is never sent to any server and is securely processed on your device.

Current Limits

  • Maximum input length: 100,000 characters

Week of the Year Calculator (ISO 8601 Week) is a 100% free, browser-based online utility. All calculations and file conversions run locally inside your browser (Local-First) without sending data to remote servers, keeping your documents and inputs strictly private.

How to Use Week of the Year Calculator (ISO 8601 Week)

  1. 1
    Input DateSelect or type date.
  2. 2
    Read ISO WeekInspect week number and canonical YYYY-Www notation.

Common Use Cases

  • Supply chain shipping weeks, retail sales reporting schedules, and corporate planning cycles
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