How it works
We use ISO 8601 week numbering. Weeks run Monday to Sunday. Week 1 is the week containing the first Thursday of the year — which is equivalent to the week containing January 4. For any date you pick, we compute the ISO week by finding the Thursday of that week, then counting how many weeks separate it from the Thursday of week 1. The 'current week' shown at the top refreshes each minute based on your device clock.
Frequently asked
Which week-numbering system do you use?open
ISO 8601. Weeks start on Monday and week 1 is the one containing the first Thursday of the year. This is what most of Europe, plus international business software, uses.
Why is the ISO week different from the US CDC week?open
The US 'epi week' starts on Sunday and week 1 is the one containing January 1. It can disagree with ISO by one week near the year boundary. This tool uses ISO.
Can a year have 53 weeks?open
Yes — years whose first day is Thursday, or leap years whose first day is Wednesday, get 53 ISO weeks.