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What Day of the Week Were You Born On?

Gizmoop Team · 5 min read · May 24, 2026

You can find out what day of the week you were born using our age calculator (instant), Zeller's congruence (math), or any modern digital calendar (Google, Apple, Outlook). The day of the week for any date is a known mathematical fact: every date has exactly one day of the week.

The Monday's Child rhyme

The famous English nursery rhyme dates from at least the 1500s:

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,
But the child born on the Sabbath day [Sunday]
Is bonny and blithe, good and gay.

The associations between weekdays and personality traits are folklore, not statistically validated. But the rhyme has charmed parents for centuries and many people look up their birth day specifically to see what the rhyme says about them.

Zeller's congruence formula

Christian Zeller, a German priest and mathematician, published his formula in 1882. It calculates the day of the week for any date in the Gregorian or Julian calendar.

For the Gregorian calendar: h = (q + floor((13(m+1))/5) + K + floor(K/4) + floor(J/4) - 2J) mod 7.

  • h: day of week (0=Saturday, 1=Sunday, 2=Monday, 3=Tuesday, 4=Wednesday, 5=Thursday, 6=Friday)
  • q: day of the month (1-31)
  • m: month, but with January = 13 and February = 14 of the previous year (March = 3, ..., December = 12)
  • K: year of the century (year mod 100)
  • J: zero-based century (floor(year / 100))

Worked example with Zeller's

What day of the week was June 15, 1990?

  1. q = 15, m = 6, year = 1990. K = 90, J = 19.
  2. h = (15 + floor((13(6+1))/5) + 90 + floor(90/4) + floor(19/4) - 2×19) mod 7
  3. = (15 + floor(91/5) + 90 + 22 + 4 - 38) mod 7
  4. = (15 + 18 + 90 + 22 + 4 - 38) mod 7
  5. = 111 mod 7 = 6
  6. h = 6 means Friday.

Sanity check: June 15, 1990 was indeed a Friday. The formula works.

The shortcut: use a calculator or app

Most modern digital calendars handle this instantly: type any historical date into Google Calendar, Apple Calendar, or Outlook and the day of the week appears. Our age calculator displays the day of the week alongside your age in years, months, and days. JavaScript and most programming languages have built-in date functions that calculate the day of the week for any date.

The math behind every modern implementation is essentially Zeller's congruence or a variant. The result is the same: every date has exactly one day of the week, computable in milliseconds.

Weekday birth-rate skew

In modern developed countries, births are slightly more common on weekdays than weekends. Roughly 1.2-1.3 times as many births happen on Tuesdays, Wednesdays, and Thursdays as on Saturdays and Sundays.

The reason: scheduled C-sections and inductions. Hospitals run skeleton crews on weekends and prefer to schedule planned deliveries on weekdays. About 30-40 percent of US births are induced or surgical, and these skew heavily toward weekdays. Spontaneous labor, by contrast, is evenly distributed across all 7 days.

So if you were born on a Tuesday or Wednesday, you have slightly more company than Sunday or Saturday babies in modern populations.

Day of the week for famous birthdays

  • Albert Einstein: Friday, March 14, 1879.
  • Marie Curie: Monday, November 7, 1867.
  • Mahatma Gandhi: Sunday, October 2, 1869.
  • Martin Luther King Jr.: Tuesday, January 15, 1929.
  • William Shakespeare: Tuesday, April 26, 1564 (baptism date; actual birth often given as April 23).
  • Michael Jordan: Sunday, February 17, 1963.
  • Beyoncé: Tuesday, September 4, 1981.
  • Elon Musk: Monday, June 28, 1971.
  • Cristiano Ronaldo: Wednesday, February 5, 1985.

Famous people are born on every day of the week. The rhyme's personality predictions are not statistically supported. But the trivia is fun.

The 28-year cycle

The day of the week for the same date cycles through every 28 years in the Gregorian calendar (with minor adjustments around century boundaries). For instance, May 23 was a Thursday in 1996, Friday in 1997, Saturday in 1998, Sunday in 1999, then Tuesday in 2000 (leap year shifts by 2). May 23 returns to a Friday in 2025 (29 years after 1996, not exactly 28 because of century leap-year rules).

Most non-century years follow the simple pattern of advancing one day per non-leap year and two days across a leap year. This is why calendars repeat in 28-year patterns and why someone born June 15, 1990 (Friday) will see the same calendar layout every 28 years going forward.

Frequently asked questions

Type your birth date into our age calculator. The day of the week appears alongside your exact age. The easier modern method beats Zeller's congruence math for accuracy and speed. Most modern calendars (Google, Apple, Outlook) also show the day of the week for any historical date.

A formula from 1882 by Christian Zeller that calculates the day of the week for any Gregorian or Julian calendar date. The formula is: h = (q + floor((13(m+1))/5) + K + floor(K/4) + floor(J/4) - 2J) mod 7, where q is the day, m is the month (with January and February counted as months 13 and 14 of the previous year), K is the year of the century, and J is the zero-based century. The result h is the day where 0=Saturday, 1=Sunday, 2=Monday, etc.

The old English rhyme: "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 / But the child born on the Sabbath day [Sunday] is bonny and blithe, good and gay." The rhyme dates from the 1500s and has many variations across English-speaking traditions.

Yes. In modern countries with scheduled inductions and C-sections, weekdays (especially Tuesdays and Wednesdays) have noticeably more births than weekends. Roughly 1.2 to 1.3 times as many births happen on weekdays as on weekends in the US and UK. Spontaneous labor is evenly distributed, but scheduled procedures favor weekdays.

No pattern; famous birth days are evenly distributed because there is no causal link. Some examples: Albert Einstein (Friday, March 14, 1879). Marie Curie (Monday, November 7, 1867). Michael Jordan (Sunday, February 17, 1963). Beyoncé (Tuesday, September 4, 1981). The rhyme's associations between days and personality are folklore, not statistically validated.

Mathematically exact for any date in the Gregorian calendar (October 15, 1582 onwards) or the Julian calendar before that. The formula is widely used in computer software for date arithmetic. The only caveat: the formula assumes the calendar conventions of the era, so dates before the Gregorian reform need careful handling depending on which country and century.

Yes. For example, October 31 was a Sunday in 1999, Tuesday in 2000, Wednesday in 2001, Thursday in 2002, Friday in 2003, Sunday again in 2004 (leap year shifts the pattern by 2 days), and so on. The day of the week cycles through a 28-year pattern (because 7 days × 4 years per leap cycle = 28) with minor century adjustments. Most dates repeat their day-of-week every 6 or 11 years.

It does not affect anyone's life, but it is a charming piece of folklore that connects modern parents and children to historical English tradition. Many parents look up their child's birth day specifically to quote the rhyme. Others find it amusing to discover what the rhyme predicts about themselves and either embrace or laugh at the description.