Week Number
Find the ISO week number for any given date, useful for scheduling, reporting, and any system that organizes time by week rather than date.
Week 35
2026
About the Week Number
This tool finds the ISO week number for any given date, useful for scheduling, reporting, and any system that organizes time by week rather than by date.
How to use
1
Enter a date, or use today's date by default.
2
View the corresponding ISO week number.
3
Change the date to check a different week.
Frequently asked questions
What is the ISO week numbering system?
ISO 8601 defines week 1 as the week containing the year's first Thursday, with weeks running Monday through Sunday.
Why do some years have 53 weeks?
Since 52 weeks only cover 364 days, a 365 or 366-day year occasionally needs a 53rd week to fully align with the ISO system.
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