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Clear, practical guides on week numbers, the ISO 8601 standard, pregnancy weeks and the calendar tools we build.

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Tools & Tips 6 min read

Calculate Week Numbers in Excel, Sheets & Python (2026)

Calculate the week number in Excel, Google Sheets, and Python with ISOWEEKNUM, WEEKNUM, and isocalendar(). Copy-paste f…

June 2, 2026 Read →