Week Number Calculator — Date Calculator
Date & TimeWeek Number Calculator is a date tool that finds the iso week number and day of year for a date.
What is it
Week Number Calculator uses browser date calculations to produce the result. It helps with repeated date checks such as day gaps, events, and weekdays.
ISO week = week containing Thursday in the ISO week-year
How to use
- 1Enter the date.
- 2Press calculate.
- 3Check the result and reference date.
Reference
| Input | Result |
|---|---|
| 2026-12-31 | finds the ISO week number and day of year for a date |
Sources & standards
- ECMAScript Language Specification - Ecma International
FAQ
What timezone does Week Number Calculator use?
It uses your browser’s local timezone for date calculations.
Is Week Number Calculator input sent to a server?
No. This tool runs in your browser and does not send input to a server.