Week Number

Gives the ISO 8601 week number for any date, along with the quarter, the day of the year and that week’s Monday to Sunday.

⏱️ Runs while this tab is open. No install, no sign-up.

Date

Uses ISO 8601 — the week containing the first Thursday is week one.

Weeks start on Monday, and the year a week belongs to is decided by which year its Thursday falls in. That means when 1 January lands on a Friday, Saturday or Sunday, it belongs to the last week of the previous year. Most companies that schedule by week number use this convention.

What this tool does

ISO 8601 week number
Quarter and day of year
Monday to Sunday of that week
Days remaining and progress

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Timer and alarm sounds may not fire if the device goes to sleep.