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ISO Week Number
Date & timeOffline-ready
ISO Week Number Calculator finds the ISO 8601 week number (1–53) for any calendar date — the standard used by European businesses, international supply chains, and date APIs. Shows the ISO year (which may differ near year-end), the first and last day of the given week, and the total number of weeks in that ISO year. Runs entirely in your browser.
Your files and inputs stay in your browser — nothing is uploaded or stored.