About this tool
Day of the Week is an in-browser date lookup that names the weekday any calendar date falls on. Pick a date and it reports the result instantly; it opens on today and recalculates the moment you choose a different date, so it works the same for past dates, upcoming deadlines, or historical events.
Alongside the weekday it shows three related figures. The day of the year counts from 1 on January 1 up to 365, or 366 in a leap year. The week number follows ISO-8601, where weeks begin on Monday and week 1 is the one containing the year's first Thursday. A weekend flag marks Saturday and Sunday. The weekday name is rendered in the page's language using your browser's built-in date formatting.
Everything is computed locally from the date you enter — nothing is uploaded, there are no accounts or tracking, and the tool keeps working offline once the page has loaded.