Week number
The current week number, or the week number of any date, in the ISO system used in Europe, the UK and Australia, and the US system.
ISO or US week numbers?
ISO 8601 weeks start on Monday, and week 1 is the week with the year’s first Thursday. Most of Europe, the UK, Australia and New Zealand use these, and so do most business systems. US-style weeks start on Sunday, and week 1 is the week that contains 1 January, so the two can differ by one.
Full lists: Week numbers 2026 · Week numbers 2027.
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