Rarest Birthdays in the US – Least Common Birth Dates

The 10 rarest birthdays in America cluster around major holidays, particularly December 25, January 1, and December 24, when elective deliveries and scheduled C-sections are routinely postponed. Analysis of more than 4.5 million U.S. birth records confirms that the rarest dates see 20 to 40 percent fewer births than a typical day.

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December 25 Is the Single Rarest Birthday in the United States

December 25 (Christmas Day) consistently ranks as the least common birthday in America across every major dataset. A widely cited analysis of 20 years of CDC birth data found that Christmas Day produces roughly 6,574 births on average, compared to the national daily average of approximately 10,000 to 11,000 births. That gap represents nearly 35 percent below normal.

Elective inductions (medically scheduled labor starts) and planned C-sections (cesarean births arranged in advance) are almost universally avoided on December 25. Hospital staffing runs at reduced holiday levels, and both patients and physicians prefer to schedule procedures away from the holiday. Only unplanned, spontaneous labors proceed on Christmas Day, which accounts for the dramatic dip in birth totals.

The reduced birth count on December 25 is not a recent development. Records stretching back to the 1970s show the same consistent pattern, confirming that cultural and institutional factors, rather than any biological cycle, are responsible.

The 10 Least Common Birthdays Ranked

The 10 rarest birth dates in the U.S. are drawn from CDC Vital Statistics data spanning 1994 to 2014, and every entry is tied to a major holiday or a cultural date that drives elective scheduling away.

Note: Thanksgiving rotates across different calendar dates each year (always the fourth Thursday of November), which is why four separate late-November dates appear in the bottom ten across a multi-year dataset.

January 1 Ranks Second for the Same Reason as Christmas

January 1 (New Year’s Day) is the second rarest birthday in the U.S., averaging roughly 7,792 births per year. The same dynamic applies: elective procedures are pushed to dates before or after the holiday, and hospital operations run on reduced New Year’s Day staffing.

New Year’s Eve also contributes in a secondary way. Expectant parents and providers who can schedule around the date sometimes choose to deliver on December 31 to claim a full calendar year of tax deductions for the dependent child. This pulls some planned births forward and leaves January 1 even lighter than it would otherwise be.

December 24 and December 26 Form a Three-Day Holiday Cluster

December 24 (Christmas Eve) and December 26 each rank in the top five rarest birthdays, creating a three-day suppression window around December 25 where birth counts drop sharply.

December 24 averages approximately 8,069 births, and December 26 averages about 8,799 births. The day before and the day after a major holiday both suffer from postponed elective deliveries and reduced physician availability, even though neither is a federal holiday in its own right.

Key Pattern: The three-day Christmas cluster covering December 24, 25, and 26 collectively represents the most concentrated and prolonged dip in U.S. birth rates of any period on the annual calendar.

July 4 Is the Only Summer Date Among the Ten Rarest Birthdays

July 4 (Independence Day) is the only summer date that ranks among the ten rarest birthdays in America, averaging roughly 8,796 births per year. Every other date in the bottom ten falls in late October or the late November through early January window.

The July 4 dip follows the same scheduling logic as winter holidays: elective inductions and C-sections are moved away from the holiday, outdoor celebrations make hospital visits less convenient for non-emergency situations, and many obstetric practices reduce their operating hours. The effect is smaller than the Christmas dip but still statistically significant.

Unlike winter holiday dates, July 4 is surrounded by days with normal or above-normal birth counts. It functions as an isolated dip rather than part of a multi-day cluster, which is one reason the magnitude of suppression is smaller.

February 29 Occupies a Legally and Statistically Unique Category

February 29 (Leap Day) is technically the rarest birthday date by definition, since it only exists once every four years, making it available only once every 1,461 days rather than once every 365.

Approximately 200,000 Americans are estimated to have a February 29 birthday, representing roughly 0.06 percent of the U.S. population. Globally, an estimated 5 million people share the Leap Day birthday. Those born on this date are sometimes called leaplings, an informal term for leap year babies.

For legal and administrative purposes, most U.S. states recognize February 28 or March 1 as the effective birthday of a leapling in non-leap years. The specific rule varies by state statute and by context, covering areas such as driver’s license expiration dates, voting age eligibility, and alcohol purchase thresholds.

February 29 is generally excluded from “rarest birthday” rankings because it is not a like-for-like comparison with dates that occur every single year. When analyzed on a per-occurrence basis it obviously produces fewer births than any other date, but on a per-year basis it simply does not exist most years.

Why Holidays Consistently Produce Fewer Births

The concentration of rare birthdays around holidays reflects two distinct mechanisms: scheduled delivery avoidance and a mild secondary effect on spontaneous labor.

Scheduled deliveries account for roughly one-third of all U.S. births through planned C-sections alone, plus an additional share through elective inductions. Both procedures can be deliberately placed on chosen dates and, equally, moved away from undesirable dates. Providers and patients share strong incentives to avoid holidays, producing a predictable trough in birth counts.

Spontaneous labor (labor that begins without medical intervention) does not cluster heavily around holidays in the same way. However, even spontaneous labor rates show mild dips on major holidays, which researchers attribute to reduced activity levels, different eating and sleep patterns during holiday gatherings, and some patients delaying hospital presentation while waiting to see whether labor intensifies before disrupting holiday plans.

Clinical Finding: Studies published in Social Science and Medicine identify elective delivery scheduling as the primary driver of the holiday birth dip, accounting for the large majority of the reduction compared to an average day. Biological factors play a much smaller secondary role.

How Scheduled Deliveries Reshaped the Entire Birth Calendar

Scheduled deliveries have fundamentally reshaped which days produce the most and fewest births since elective procedure rates began rising sharply in the 1990s. Before widespread elective scheduling, birth counts were more evenly distributed throughout the year.

The U.S. C-section rate climbed from roughly 5 percent in 1970 to a peak of 32.9 percent in 2009, before stabilizing at around 32 percent in recent years. Approximately 1 in 3 American babies is now born via C-section, and a meaningful share of those births are scheduled on specific chosen dates.

Elective induction rates followed a similar trajectory. The national induction rate (the share of labors started artificially using medications or mechanical procedures) rose from approximately 9 percent in 1990 to over 25 percent in recent years according to CDC data. Each induction represents a birth that can be deliberately moved around calendar preferences.

The combined result is a birth calendar that reflects both underlying reproductive biology and a significant overlay of human scheduling behavior.

Day-of-Week Patterns Mirror the Holiday Effect

Tuesdays and Wednesdays produce the most births of any days of the week in the United States, while Sundays produce the fewest, and this weekday gap is driven by the same scheduling logic as the holiday dip.

Planned C-sections and elective inductions are almost exclusively scheduled on weekdays, when full hospital staffing and standard operating room schedules are available. Weekend births consist predominantly of spontaneous labors that happen to begin on a Saturday or Sunday.

The gap between the highest-birth weekday (Tuesday) and the lowest-birth day (Sunday) can reach as large as 30 percent in absolute birth counts, a difference comparable in scale to the holiday dips that define the rarest birthday list.

September Dominates the Most Common Birthday Rankings

September is the peak birth month in the United States, and dates in early to mid-September consistently rank as the most common birthdays in the country. September 9 is the most frequently cited single most common birthday based on multi-decade birth data.

The September peak traces back approximately nine months to December, when conception rates rise during the holiday season. The combination of winter holidays, reduced work stress, and more time spent at home correlates with elevated conception activity from late November through early January.

The 5 most common birthdays in the U.S. based on the same CDC and Social Security Administration datasets:

1. September 9
2. September 19
3. September 12
4. September 17
5. September 10

The contrast between a peak September date (approximately 12,000 average annual births) and the rarest date, December 25 (6,574 births), represents close to a 2 to 1 ratio in birth volume between the most and least common birthdays on the calendar.

Monthly Birth Patterns Across the Full Calendar Year

Month-level patterns offer a broader view of how birth timing distributes across all 12 months.

December is the lowest-volume birth month overall when adjusted for the number of days in the month, driven by the powerful suppression effect of the Christmas cluster in the final week of the year.

Why October 31 Appears Despite Not Being a Federal Holiday

October 31 (Halloween) ranks among the ten rarest birthdays in the U.S., averaging approximately 9,034 births, roughly 11 percent below the daily average, even though Halloween carries no federal holiday designation.

Research published in Social Science and Medicine in 2011 found a statistically significant decrease in births on Halloween and a corresponding increase on Valentine’s Day (February 14). The study concluded that cultural associations with dates, not just official holiday status, influence elective scheduling decisions. Some parents prefer not to deliver on a date culturally associated with dark or frightening themes, and some providers adjust elective schedules to accommodate those preferences.

Valentine’s Day, by contrast, shows a mild 3 to 5 percent above-average birth count, reflecting a preference among some parents for the romantic connotations of the date. This Valentine’s effect is small but statistically detectable across large datasets.

Geographic Variation Across U.S. States

The national pattern holds in every region, but the magnitude of the holiday birth dip varies meaningfully across states by roughly 5 to 10 percentage points depending on local factors.

States with large Catholic populations, including Massachusetts, New Mexico, and Rhode Island, show particularly strong Christmas Day dips, consistent with the cultural weight of the holiday in those communities.

States with higher rates of home births and midwife-attended deliveries, such as Oregon and Vermont, show slightly less pronounced holiday dips because elective hospital scheduling is not the only delivery pathway available to patients.

Urban versus rural differences are also measurable. Large metropolitan hospitals with robust holiday staffing show smaller holiday dips than rural hospitals that rely on a smaller pool of on-call physicians. In rural areas where the nearest hospital is a significant distance away, patients may also labor at home longer before presenting, creating different timing patterns independent of the holiday effect.

The Data Sources Behind Rarest Birthday Research

The most authoritative publicly available data on U.S. birth dates comes from the CDC National Center for Health Statistics (NCHS), which publishes annual birth microdata through its Vital Statistics program. Researchers have used this multi-decade dataset to identify every pattern described in this article.

A widely referenced independent analysis was published by FiveThirtyEight in 2014, using 20 years of Social Security Administration birth records covering 1994 to 2014. That work produced the widely circulated heat map of U.S. birthday frequency and is the source for many specific per-date birth count figures cited in rarest birthday discussions.

Harvard-affiliated economist Amitabh Chandra and colleagues published peer-reviewed research demonstrating that elective scheduling is the mechanistic explanation for holiday birth dips, ruling out seasonal fertility variation as the primary cause. The consistency of findings across CDC microdata, Social Security Administration records, and independent hospital-level studies makes the December 25 ranking as rarest U.S. birthday one of the most robustly supported findings in birth data research.

Cultural Preference Now Shapes Birth Timing as Much as Biology

Cultural preference plays a measurably larger role in birth date selection than most people realize, and its influence has grown directly alongside the rise of scheduled deliveries in the late 20th century.

Studies show that providers and patients jointly influence date selection in ways that would have been impossible when nearly all births were spontaneous. Providers tend to avoid holidays for logistical reasons including reduced staffing and personal plans. Patients planning elective C-sections sometimes request specific dates based on family significance, numerological preference, or the desire to avoid dates associated with difficult events or holidays.

The result is a birth calendar that simultaneously reflects biological reproductive rhythms (the September peak from December conceptions) and a significant overlay of human scheduling preference (holiday troughs, Tuesday peaks, Valentine’s Day bumps, Halloween dips). Understanding which birthdays are rarest therefore requires understanding both the physiology of conception and the sociology of modern obstetric scheduling.

FAQs

What is the rarest birthday in the United States?

December 25 (Christmas Day) is the rarest birthday in the United States, averaging approximately 6,574 births per year according to CDC Vital Statistics data spanning two decades. This is roughly 35 percent below the national daily average of about 10,000 to 11,000 births. The dip is caused almost entirely by the postponement of elective inductions and scheduled C-sections around the holiday.

What is the second rarest birthday in America?

January 1 (New Year’s Day) is the second rarest birthday in the U.S., averaging about 7,792 births per year. Like Christmas Day, the low count reflects hospital scheduling practices that push elective deliveries away from the federal holiday. Some planned births are also moved to December 31 for tax dependency reasons, further reducing the January 1 total.

Is February 29 the rarest birthday?

February 29 (Leap Day) is technically the rarest birth date because it only occurs once every four years, appearing on the calendar just once every 1,461 days. However, when comparing dates that all occur every single year, December 25 produces fewer births on a per-occurrence basis. Roughly 200,000 Americans are estimated to have a February 29 birthday.

Why are there fewer births on holidays?

Fewer births occur on holidays primarily because elective C-sections and scheduled inductions are deliberately moved away from holiday dates by both physicians and patients. Approximately 1 in 3 U.S. births is via C-section, and a large additional share involves elective induction, giving families and providers meaningful scheduling flexibility. Reduced holiday staffing in hospitals also makes providers less likely to initiate elective procedures on those dates.

What are the most common birthdays in the United States?

The most common birthdays in the U.S. fall in September, with September 9 most frequently cited as the single most common birth date based on 20 years of CDC and Social Security Administration data. The September peak reflects conceptions occurring around the December holiday season, approximately nine months earlier. September 9 averages close to 12,000 births, compared to roughly 6,574 for December 25, the rarest date.

Does Halloween really have fewer births than average?

Yes, October 31 (Halloween) averages approximately 9,034 births, about 11 percent below the U.S. daily average. Research published in Social Science and Medicine found a statistically significant Halloween dip and a corresponding Valentine’s Day uptick, confirming that cultural associations with dates influence elective delivery scheduling decisions even for dates that carry no federal holiday status.

Which day of the week has the fewest births?

Sunday has the fewest births of any day of the week in the United States, followed closely by Saturday. The weekend dip exists because elective C-sections and scheduled inductions are performed almost exclusively on weekdays when full hospital staffing and operating room access are available. Tuesday and Wednesday consistently produce the most births, with a gap of up to 30 percent between the highest and lowest weekday totals.

How many Americans share a December 25 birthday?

Given an average of approximately 6,574 births per December 25 and a current U.S. population of roughly 330 million, an estimated 1 to 1.5 million Americans may have a December 25 birthday when accounting for population growth and historical birth rate changes. This is noticeably fewer than the number of Americans sharing any given September birthday, confirming the statistical rarity of the Christmas birthday.

Are rare birthdays more common in certain U.S. states?

The national pattern holds across all regions, but the magnitude of the holiday birth dip varies by roughly 5 to 10 percentage points by state. States with higher rates of home births and midwife-attended deliveries, such as Oregon and Vermont, show smaller holiday dips. States with higher hospital birth rates and large populations that observe major religious holidays more observantly show stronger dips on dates like December 25.

Which Thanksgiving dates appear on the rarest birthday list?

November 23, 24, 25, and 27 all appear in the bottom ten rarest birthdays in multi-year analyses because Thanksgiving rotates across different calendar dates each year as the fourth Thursday of November. Over a 20-year dataset, each of these dates accumulates several years of Thanksgiving-suppressed birth counts, pushing all four into the bottom ten despite none of them being fixed federal holiday dates on the calendar.