Week Number to Date
Enter an ISO 8601 week number, year, and weekday to instantly find the matching calendar date. Also shows the Monday and Sunday of that week.
Input
Result
Enter an ISO year, week number, and day of the week.
How it works
- ISO 8601 week numbers begin on Monday, and the first week of the year is the one containing its first Thursday. Because January 4 always falls in week 1, the tool uses it as the anchor for every calculation.
- Just choose a week-year, week number, and weekday, and the matching calendar date is shown large, along with the Monday and Sunday that bracket the week.
- At the start or end of the year, the calendar year can differ from the ISO week-year. For example, if January 1 is a Friday it belongs to the final week of the previous year. This tool calculates based on the week-year you enter.
- Some years end at week 52 and others at week 53. The input field shows the total number of weeks for the chosen year, and any out-of-range week number is flagged automatically.
- If you need to go the other way, use the companion tool that converts a date into its ISO week number alongside this calculator.
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