Even/Odd Week

According to the ISO 8601 standard, week 1 is the week containing the year's first Thursday. Weeks start on Monday and end on Sunday. A week is even if its number is divisible by 2 (weeks 2, 4, 6...) and odd otherwise (weeks 1, 3, 5...).

The week changes every Monday at midnight. If you are in an even week, the next one will be odd, and vice versa. This cycle alternates every 7 days, 52 times per year (53 in some years like 2026).

Even and odd weeks are widely used for shared custody arrangements, rotating team schedules, alternating waste collection, and any biweekly rotation system. Our tool lets you instantly check whether any date falls on an even or odd week.

The answer appears in under a second — no sign-up, no account, no ads. Pick a date and get an instant result. The tool is completely free, available in 4 languages (French, English, German, Dutch) and based on the ISO 8601 standard used across Europe — the same standard as your professional or school calendar.

The iPhone app includes a home screen widget: without even unlocking your phone, you know at a glance whether it's an even or odd week. That's the number one feature. The app also works fully offline — no internet connection needed — updates automatically every Monday, and lets you check any date in seconds. Perfect for shared custody: never wonder again.