Day of Week Calculator

Find what day of the week any date falls on

Enter a Date

Monday

Quick References

Related Tools

Calendar Date Difference Week of Year Today's Date

Frequently Asked Questions

Enter any date into our calculator and click "Find Day." The tool instantly shows the day of the week (Monday through Sunday), the full formatted date, and what day of the year it is.

Yes. The calculator works for any valid date supported by your browser's date picker. You can check historical dates (like July 4, 1776) or future dates (like January 1, 2050) with equal accuracy.

Simply enter your birth date into the calculator. It will tell you the exact day of the week you were born, along with the day number of the year.
Embed This Calculator on Your Website
Written & Reviewed by Experts
SM
Author

Sarah Mitchell, CPA

Certified Public Accountant • 12+ yrs payroll & workforce analytics

Specializes in time management, payroll compliance, and workforce optimization. Helped 500+ businesses streamline time-tracking.

DC
Fact-Checker

David Chen, MBA

Finance & Operations • MBA, Wharton

Specializes in financial modeling, regulatory compliance, and data accuracy verification across payroll and tax systems.

Updated Apr 4, 2026 50+ calculators Expert reviewed
Editorial Policies About Us

Day of Week Calculator: Algorithms, History, and Cultural Significance

What day of the week was July 4, 1776? What day will January 1, 2050 fall on? What day were you born? These are surprisingly common questions, and answering them without a calculator requires either a calendar at hand or knowledge of mathematical algorithms that have fascinated mathematicians for centuries. Our Day of Week Calculator gives you the answer instantly for any date—past, present, or future.

Zeller's Formula: The Math Behind Day-of-Week Calculation

Zeller's Congruence: h = (q + ⌊13(m+1)/5⌋ + K + ⌊K/4⌋ + ⌊J/4⌋ − 2J) mod 7, where q = day of month, m = month (March=3 through February=14), K = year of century, J = century. The result h maps to a day: 0=Saturday, 1=Sunday, 2=Monday, etc.

Developed by Christian Zeller in the 1880s, this formula allows you to compute the day of the week for any Gregorian calendar date using only arithmetic. January and February are treated as months 13 and 14 of the previous year, which simplifies the leap year adjustment. While elegant, it's error-prone for manual calculation—one reason tools like our calculator exist.

The Doomsday Algorithm

Mathematician John Horton Conway developed a simpler mental method in 1973 called the Doomsday Algorithm. The key insight is that certain dates always fall on the same day of the week within any given year—Conway calls this the "Doomsday" of that year:

  • The last day of February (28th or 29th) is always on Doomsday
  • 4/4, 6/6, 8/8, 10/10, and 12/12 are always on Doomsday
  • 7/11 and 11/7 are always on Doomsday
  • The "I work 9-5 at 7-11" mnemonic: 5/9, 9/5, 7/11, 11/7 all share Doomsday
2026 Doomsday: The Doomsday for 2026 is Saturday. This means February 28, April 4, June 6, August 8, October 10, and December 12 all fall on Saturday in 2026. From any of these anchor dates, you can count forward or backward to find the day for any other date in the year.

Worked Examples

Example 1 — Independence Day: July 4, 1776 was a Thursday. The Declaration of Independence was adopted on a Thursday, and the Liberty Bell (according to tradition) rang out across Philadelphia that day.
Example 2 — Your Birthday: If you were born on December 25, 1995, the calculator shows that was a Monday. Christmas Day fell on a Monday that year—a "Monday child" according to the nursery rhyme.
Example 3 — Future Date: January 1, 2030 falls on a Tuesday. If you're planning a New Year's celebration, you'll know it's a weekday—expect a quieter party than a weekend New Year's.

Famous Dates and Their Days of the Week

Event Date Day of Week
US Declaration of IndependenceJuly 4, 1776Thursday
Titanic sinkingApril 15, 1912Monday
D-Day (Normandy invasion)June 6, 1944Tuesday
Moon landingJuly 20, 1969Sunday
Fall of Berlin WallNovember 9, 1989Thursday
Y2K / MillenniumJanuary 1, 2000Saturday
September 11 attacksSeptember 11, 2001Tuesday
iPhone announcementJanuary 9, 2007Tuesday

Born on Which Day: Superstitions and Folklore

Across many cultures, the day of the week you were born is believed to influence your personality. The most famous English tradition comes from the nursery rhyme "Monday's Child":

  • Monday's child is fair of face
  • Tuesday's child is full of grace
  • Wednesday's child is full of woe
  • Thursday's child has far to go
  • Friday's child is loving and giving
  • Saturday's child works hard for a living
  • Sunday's child is bonny, blithe, good, and gay

In Akan culture (Ghana), children are given a "day name" based on their birth day—Kwame for Saturday boys, Ama for Saturday girls, Kofi for Friday boys, and so on. Former UN Secretary-General Kofi Annan's first name means "born on Friday." In Thai tradition, each day of the week has an associated color, and Thais often wear their birth-day color on their birthday.

Calendar Note: For dates before September 14, 1752 (in Britain and its colonies), the Julian calendar was in use. The Gregorian calendar correction skipped 11 days, so dates before this transition may produce different results depending on which calendar system is assumed. Our calculator uses the proleptic Gregorian calendar for all dates.

Our Day of Week Calculator is free, instant, and works for any date. Try it for birthdays, historical events, or future planning. For related tools, explore our Calendar, Week of Year, Date Difference Calculator, and Today's Date.