The Most Common and Rarest Birthdays, From 20 Years of Data
September 9 tops the list and Christmas Day is the rarest regular date. Here is why holidays, weekends and December nights shape when babies are born.
By The Xilfy Team Updated 3 min read
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Zodiac sign, Chinese zodiac, birthstone, generation and how rare your birthday is, for any date
Birthdays aren't spread evenly through the year. In US births data from 1994 to 2014, the most popular day of the year saw nearly twice as many births as the least popular. Holidays, hospital schedules and the calendar nine months earlier all leave a mark. Here's what the numbers show.
The most common birthdays
All of the top ten are in September, apart from one in July:
| Rank | Date | Average births that day |
|---|---|---|
| 1 | September 9 | 12,344 |
| 2 | September 19 | 12,285 |
| 3 | September 12 | 12,282 |
| 4 | September 17 | 12,201 |
| 5 | September 10 | 12,190 |
| 6 | September 20 | 12,162 |
| 7 | July 7 | 12,147 |
| 8 | September 15 | 12,126 |
| 9 | September 16 | 12,114 |
| 10 | September 18 | 12,112 |
Count back nine months from mid-September and you land in mid to late December, the holiday season. More time off, colder nights and end-of-year celebrations all seem to play a part.
The rarest birthdays
| Date | Average births | Why |
|---|---|---|
| February 29 | 10,512 (once every 4 years) | Leap day only exists in leap years |
| December 25 | 6,601 | Christmas Day |
| January 1 | 7,827 | New Year's Day |
| December 24 | 8,103 | Christmas Eve |
| July 4 | 8,825 | Independence Day |
| January 2 | 9,356 | Day after New Year |
| December 26 | 9,599 | Day after Christmas |
| November 23–27 | 9,770–10,053 | Thanksgiving week |
The average day had 11,175 births. On Christmas Day there were only about 59% as many.
Why holidays have fewer births
Babies arrive when they're ready, but a large share of US births are scheduled: planned caesarean sections and induced labours. Hospitals and families avoid booking these on public holidays, so they move to the days just before or after. The same pattern explains why Halloween (October 31) and April 1 rank near the bottom too. Some parents would rather not have a spooky or prank birthday.
The weekday effect is even bigger
The same scheduling shows up across the week. Weekends have far fewer births than weekdays:
Tuesday is the busiest day to be born and Sunday the quietest, with about 40% fewer births than Tuesday. Your own birthday rank depends partly on how often your date has fallen on a weekend in recent years.
How rare is your birthday?
Our Birthday Report ranks every date from 1 to 366 using this data. It also shows your zodiac sign, Chinese zodiac animal, birthstone, birth flower, generation and the weekday you were born. Try the most common birthday, September 9, or the rarest regular day, December 25.
Frequently asked questions
What is the most common birthday?
In US births from 1994 to 2014, September 9 had the most births on average, followed by September 19 and September 12.
What is the rarest birthday?
February 29 is the rarest, because it only happens once every four years. Of the dates that come every year, December 25 is the rarest, then January 1 and December 24.
Which month has the most births?
September, with August and July close behind. January has the fewest births per day.
Is this data the same in other countries?
The holiday dip and the late-summer peak appear in many countries, but the details differ. Countries with different holidays, or with fewer scheduled births, show weaker patterns.
Data: US births from the CDC National Center for Health Statistics (1994–1999) and the Social Security Administration (2000–2014), compiled by FiveThirtyEight (CC BY 4.0). Averages are births per occurrence of each date.
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