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Day of the Week Calculator

What day any date falls on, past or future.

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This date in other years

The weekday shifts by one each year, or two across a leap year.

YearWeekdaySame as now?

The Doomsday rule

John Conway's mental algorithm. In any given year, a set of dates all fall on the same weekday — called that year's doomsday: 4/4, 6/6, 8/8, 10/10, 12/12, the last day of February, and 9/5, 5/9, 7/11, 11/7. Learn the doomsday for a year and you can reach any other date by counting forwards or backwards in sevens from the nearest anchor.

The doomsday for this date's year is —.

Day of the week

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About this date

Day of the year—
ISO week number—
Quarter—
Leap year—

Relative to today

Days away—
Weeks away—

—

Next years this date falls on the same weekday

A normal year is 52 weeks plus a day, so a given date advances one weekday each year and two across a leap year. The whole Gregorian calendar repeats on a 400-year cycle, which is why the gaps between repeats follow a 6, 11, 5 pattern rather than a fixed interval.

Quick Tool Overview

The Day of the Week Calculator finds which weekday any date falls on, past or future, with the ISO week number, day of the year, days away, and the coming years in which that date returns to the same weekday.

What it does
Finds the weekday for any date
You give it
A single date
You get back
The weekday, week number, day of year and repeats
Best for
Birthdays, historical dates and planning ahead
Calculators Free, unlimited use No sign-up Runs in your browser

About the Day of the Week Calculator

Find which day of the week any date falls on, from centuries past to far into the future. Alongside the answer you get the ISO week number, the day of the year, how many days away it is, and the years when that same date will fall on the same weekday again.

The Gregorian calendar repeats on a 400-year cycle, which is why the same date returns to the same weekday in a pattern of 6, 11 and 5 year gaps rather than a fixed interval — leap years break the regularity. The page also explains the Doomsday rule, a mental algorithm for working out any weekday without a calculator, since that is what people are usually curious about once they have the answer.

Key features of the Day of the Week Calculator

Any date, any era

Centuries past through to far into the future, using the proleptic Gregorian calendar.

Repeat years listed

The 6, 11 and 5 year pattern in which a date returns to the same weekday, which leap years disrupt.

ISO week number

The standard used across Europe and in most business software, where week 1 holds the first Thursday.

Doomsday rule explained

Conway's mental algorithm for working out any weekday without a calculator.

Leap year flagged

Along with the day of the year, which shifts by one after February in a leap year.

How to use the Day of the Week Calculator

  1. 1

    Choose a date

    Any date, past or future. Birthdays and historical dates both work.

  2. 2

    Read the weekday

    Along with the full formatted date in your locale.

  3. 3

    Check the details

    ISO week number, day of the year, days away and leap year status.

  4. 4

    See the repeats

    The next years in which that date falls on the same weekday.

Frequently asked questions

Enter your birth date and the calculator returns the weekday, along with how many days ago it was and which upcoming birthdays fall on the same day.

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