Week Number Calculator
Find the ISO 8601 week number for any date, along with its week year and the Monday–Sunday range it belongs to.
Result
- ISO week
- Week 25
- ISO week year
- 2026
- Day of week
- Saturday
- Week range
- 2026-06-15 → 2026-06-21
Saturday, June 20, 2026 is in ISO week 25 of 2026 (2026-06-15 to 2026-06-21).
How to use
- Pick any date.
- Read the ISO week number, its week year, and the Monday–Sunday range.
Example
January 1, 2024 falls in ISO week 1 of 2024. That ISO week runs from Monday, January 1, 2024 to Sunday, January 7, 2024.
December 31, 2023 falls in ISO week 52 of 2023.
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Frequently asked questions
Calcadian calculators are for general planning and informational use. Please verify critical deadlines, legal, payroll, tax, HR, or official requirements with the relevant authorities or a qualified professional.