Current ISO Week

See the current ISO week from your device clock, including the ISO week-year and Monday-to-Sunday date range.

The calculation uses your local calendar date but applies ISO 8601 week rules. Nothing is uploaded.

The calculation uses your local calendar date but applies ISO 8601 week rules. Nothing is uploaded.

Current calendar week

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ISO identifier ----W--

Monday – Sunday

ISO weeks run from Monday through Sunday.

Device date and time

Local calendar date

Detected timezone

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ISO week-year

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Week date range

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Day within ISO week

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The result follows this device clock and timezone, including daylight-saving changes.

What this tool does

Shows the current ISO week number and its separate ISO week-year from the device’s local date.

Shows the corresponding Monday-to-Sunday range, local time and detected timezone without a server request.

How to use the tool

  1. Open the tool and check the week number and ISO identifier.
  2. Use the date range to see the Monday and Sunday belonging to that ISO week.
  3. Check the detected timezone when comparing results across locations.
  4. Refresh after changing the device date, time or timezone.

Useful applications

  • Planning work, releases, reports and recurring weekly meetings.
  • Checking which dates belong to a referenced calendar week.
  • Avoiding ambiguity near New Year when the ISO week-year differs from the calendar year.
  • Comparing a local result with schedules that use ISO week notation.

Notes and limitations

  • ISO weeks begin on Monday, and week 1 is the week containing the year’s first Thursday.
  • An ISO week-year can differ from the calendar year for dates near the start or end of December.
  • The calculation uses the device’s local calendar date, not a server location.
  • An incorrect device clock or timezone produces an incorrect result.

Frequently asked questions

When does an ISO week start?

Monday. Every ISO week contains exactly seven days and ends on Sunday.

What is the ISO week-year?

It is the year associated with the ISO week. Around New Year it may differ from the date’s calendar year.

Why can December 31 belong to week 1 of the next year?

ISO week 1 is defined by the week containing the first Thursday, so boundary dates can belong to the adjacent ISO week-year.

Which timezone is used?

The timezone currently resolved by your browser and device settings.

Is my date or timezone uploaded?

No. The calculation and formatting run locally in the browser.

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