Your date of birth

About What Day Was I Born

Enter your date of birth and this tool will instantly tell you which day of the week you were born on, your current age in years, months, and days, and how many days remain until your next birthday.

How the day of the week is calculated

The calculation uses the Tomohiko Sakamoto algorithm, a compact formula that correctly determines the day of the week for any date in the Gregorian calendar, accounting for leap years and century adjustments.

Day of the week facts

Monday — the most common birth day in many countries, as hospitals schedule more planned births on weekdays
Sunday — statistically the least common birth day due to fewer planned procedures
Any day — for natural births, the distribution is fairly even across all seven days

What else does it show?

Alongside your birth day, the tool displays your precise age broken down into years, months, and days, plus a countdown to your next birthday so you always know how long to wait.

Day of the week in history and culture

The day of the week has cultural significance in many traditions. In astrology, each day is associated with a celestial body (Monday-Moon, Tuesday-Mars, Wednesday-Mercury, Thursday-Jupiter, Friday-Venus, Saturday-Saturn, Sunday-Sun). Many cultures have beliefs about the significance of the day of birth. The nursery rhyme "Monday's child is fair of face" reflects this tradition.

Monday — from Old English Mōnandæg (Moon's day)
Tuesday — from Tīwesdæg, named for Tiw (Norse god of war, equivalent to Roman Mars)
Wednesday — from Wōdnesdæg, named for Woden (Odin); Mercredi in French from Mercury
Thursday — from Þūnresdæg (Thor's day); Jeudi in French from Jupiter
Friday — from Frīgedæg (Frigg's day); Vendredi in French from Venus

Frequently Asked Questions

What is the most common birthday?

In the US, September 9 is statistically the most common birthday, followed by other dates in September. This is likely because December and January are peak conception months. The least common birthdays are on public holidays like Christmas Day and New Year's Day.

What day of the week has the most births?

Tuesday is statistically the most common birth day in many countries, as most planned C-sections and inductions happen on weekdays. Fewer births occur on weekends due to reduced hospital staffing.

How is the day of the week calculated from a date?

The calculator uses the Gregorian calendar algorithm (also known as Zeller's congruence or Tomohiko Sakamoto's algorithm) to determine the exact day of the week for any historical date. It correctly accounts for leap years going back centuries.

Does it work for dates before 1900?

Yes — the Gregorian calendar algorithm works for any date back to 15 October 1582, when the Gregorian calendar was first adopted. Dates before that used the Julian calendar, which has different rules, so very old historical dates may not match historical records.

What day of the week is the most common birthday?

Tuesday and Wednesday are statistically the most common days to be born, while weekends have lower birth rates due to fewer planned inductions and caesarean sections being scheduled on Saturdays and Sundays.

What Day Was I Born?