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Day of the Week Calculator: What Day Is Any Date?

This free day of the week calculator tells you which weekday any date falls on, past or future. It also shows the day of the year, ISO week number, quarter and whether the year is a leap year.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

Every date falls on one of seven weekdays, and the pattern is easy to calculate with the right method. People ask it to find the day they were born, to plan events and to check calendars. The week number and day of year are useful for work reports and logistics.

Pick any date and read all of these facts at once.

How to Use This Tool

  1. Pick a date with the date box.
  2. Press Find.
  3. Read the weekday and the other facts.
  4. Change the date to compare.

How the Calculation Works

The date becomes a day count from a fixed starting point. The weekday is that count modulo seven, with a fixed offset. The day of the year is the count minus the count of 1 January plus one. The ISO week uses the week containing the Thursday of that week to decide which year it belongs to.

Worked Example

2 November 2026 is a Monday, the 306th day of the year, in ISO week 45, in the fourth quarter. 2026 is not a leap year. 15 August 1947 was a Friday.

Common Uses

  • Finding the weekday you were born.
  • Planning events and meetings.
  • Work reports by week number.
  • Checking historical dates.

Tips and Common Mistakes

  • Use ISO format 2026-11-02 if the date box is empty.
  • Week numbers start on Monday in the ISO system.
  • The tool uses the Gregorian calendar throughout.

Next, you may need the age calculator, leap year checker, date add and subtract calculator, zodiac sign finder.

Everything runs in your browser. Nothing you type is uploaded, stored or sent to any outside service.

Frequently Asked Questions

Count the days from a known date. The tool converts the date to a day number and uses the fact that day numbers repeat every seven days.
The ISO 8601 standard numbers weeks starting on Monday, and week 1 is the week with the first Thursday of the year. It can differ from other week numbering systems.
Yes, from year 1, using the proleptic Gregorian calendar. Dates before 1582 would have used the Julian calendar in Europe, so they may differ from old records.
Enter your birth date and read the weekday in the first row.

Disclaimer: results are calculated in your browser from the numbers you enter. Check important results before you rely on them for money, health, safety or legal decisions.