What Week Is It?
Today's week number, Monday to Sunday, and any other date's.
Runs entirely in your browser
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The page opens on today: the week number, the Monday and Sunday it runs between, and where today sits in the year, its day number and the days left. Pick any other date for its week instead.
The big number is the ISO 8601 week, the one calendars in Europe and most software use: weeks from Monday, week 1 holding the year's first Thursday. The US count, with weeks from Sunday and week 1 holding 1 January, is shown beneath, because the two differ by one for much of the year.
How to use it
- Read today's week number at the top.
- Pick another date to see its week instead.
Questions
Why do two calendars disagree about the week number?
They count differently. ISO 8601 starts weeks on Monday and makes week 1 the first one with a Thursday in it; the common US count starts on Sunday and makes week 1 the one with 1 January. Both are shown here.
How many weeks are in a year?
52 or 53 ISO weeks: a year has 53 when it starts on a Thursday, or on a Wednesday in a leap year. 2026 has 53.
Is anything sent anywhere?
No. The dates are worked out in this tab, in WebAssembly, by a page that is not allowed to open a network connection. Nothing you type is stored or sent.
Other date questions
The same calculator, opened on another question. All four are a tap away on each.
Your data stays on your device
Everything above runs inside your browser as WebAssembly compiled from Rust. Nothing you type is uploaded, logged or stored on a server. You can load this page once, go offline, and it still works.
This page makes no requests at all, to anywhere. That is not a promise in the copy: it is a Content-Security-Policy header your browser enforces, and connect-src on it is none. Open the network tab and watch nothing happen.