ISO week calendar

Week numbers and exact dates

Find the current ISO week number and browse exact Monday-to-Sunday dates for every week in 2026 and 2027.

Current ISO week

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Browse by year

Week numbers 2026All ISO weeks and date ranges →Week numbers 2027All ISO weeks and date ranges →

How ISO week numbers work

ISO weeks start on Monday and end on Sunday. Week 1 is the week containing the year’s first Thursday, so the first few days of January can belong to the previous ISO week-year.

Use the individual week pages when you need the exact Monday–Sunday dates for a schedule, timesheet or project plan.