Find the week-of-year for any date — ISO & simple modes supported.
What this tool does
Enter or paste a date to instantly calculate which week of the year it belongs to. Supports both ISO week numbering and simple week numbering.
Tip: You can paste multiple dates — one per line.
FAQ
1. What is an ISO week?
ISO weeks start on Monday, and week 1 is the week containing January 4th.
2. Why does the week belong to a different year?
ISO week years are different from calendar years and may shift near New Year’s.
3. Can I paste multiple dates?
Yes, simply paste one date per line.
4. Which formats are supported?
YYYY-MM-DD, DD/MM/YYYY, and many browser-recognized formats.
5. Is it accurate for all years?
Yes, the calculation follows ISO-8601 and simple week rules consistently.