Day of the Week Calculator

How to use

1. 1Pick a date with the date picker, or type a year between 1 and 9999 into the field.
2. 2Use the Today, Yesterday, Tomorrow, plus or minus 1 week buttons to nudge the date by common amounts, or click a famous-date preset to jump straight to it.
3. 3Read the Weekday card for the full weekday name, the long-form date with an ordinal suffix, and a relative label like today, tomorrow, in 12 days, or 4,562 days ago.
4. 4Use the metadata rows for the ISO 8601 weekday number, Sunday-first index, day of year, ISO week number, and leap year flag. Each row has its own Copy button.
5. 5Pick a target weekday in the Find the next or previous weekday section to see the next and previous occurrence of that weekday relative to the date above. Tick Allow the same day if you want today to count when it already matches.
6. 6Click Copy full report to copy a multi-line summary you can paste into notes, a spreadsheet, or a calendar entry.

About this tool

Day of the Week Calculator answers the everyday question that brings searchers in: what weekday is (or was) a given date. Pick a date with the native picker, type any year between 1 and 9999, or jump to a famous date preset, and the tool returns the full weekday name (Monday through Sunday), the short name (Mon, Tue, ...), the ISO 8601 weekday number (1 = Monday, 7 = Sunday), and the Sunday-first index that JavaScript's getDay returns (0 = Sunday, 6 = Saturday). Alongside the weekday it shows the day of the year (1 to 365 or 366), days remaining in the year, the ISO 8601 week number with the correct ISO week-year (so dates near year boundaries are not miscounted), and whether the year is a leap year on the proleptic Gregorian calendar. A reverse lookup lets you pick a target weekday (Monday through Sunday) to see when it next falls on or after the chosen date and when it last fell on or before that date, with an option to count the same day if it already matches. Common questions this covers: what day of the week was I born, what day was January 1 of any year, what day will my anniversary fall on next year, which Friday comes after a specific deadline, and how many days into the year a given date sits. The arithmetic uses UTC accessors throughout so a Friday in New York is the same Friday in Tokyo and daylight saving transitions never shift the answer. Nothing is uploaded; the date you pick stays on your device.

Free to use. Works in your browser. No signup, no login.