December in the birth records
December accounts for 5,194,432 births, or 8.35% of the 62,187,024 records in the SSA 2000–2014 sample. Within this month, December 19 is the most common date, ranked #4 nationally. December 25 has the fewest total records and ranks #365. The table above includes all 31 dates, not just those two extremes.
What makes this month worth a closer look
December 25 has the fewest recorded births among the dates that occur every year in this dataset. December 24 is low too. These fixed dates can be compared directly with the ordinary days around them, rather than treating every December birthday as equally unusual.
Leap day still ranks below Christmas when counting all birth records, because February 29 exists only four times in the sample. If someone asks for the rarest “annual” birthday, December 25 answers that narrower question. The year-end calendar continues into January 1, another low-count date. The rarest-birthday list places all of these on the same scale and explains the distinction.
Read your row and make a card
Rank #1 is most common across all 366 dates. “1 in” divides all birth records by the records for that specific date; the daily-average column divides by the number of times the date occurred. A higher “rarer than” percentage means more other dates had higher counts. These are different ways of describing the same historical sample, not estimates of everyone alive today.
Select your date in the table to open the birthday calculator. Save a portrait or landscape result, or combine it with your name. The complete methodology and original FiveThirtyEight source stay available for anyone who wants to check the numbers.