What were the most common birthdays in 1969–1988, and what changed since?

Published by Birthday Traffic · September 15, 2026 · Sources and method

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• September 16most common birthday, 1969–198810,646 births per occurrence; #9 in 1994–2014
• December 25least common, 1969–19887,689 per occurrence, leap day aside
• 84% → 66%weekend level, then and nowSaturday and Sunday against a weekday, per day
• 1.38× → 1.87×busiest date over quietest365 every-year dates, by share of the year

In the daily file for 1969–1988, 70,485,508 recorded U.S. births over 20 complete years, the most common birthday was September 16 and the least common, leap day aside, was December 25. September led then as it does now. What changed by 1994–2014 is the shape of the week: a Saturday or Sunday recorded about 84% of a weekday’s births then and about 66% later, and the busiest every-year date was 1.38 times the quietest then and 1.87 times later. The series records counts.

The most common birthdays, 1969–1988

Ranked by total recorded births, the same rule as the 1994–2014 ranking the rest of this site uses; the per-occurrence column divides by the number of years the date occurred, which matters only for February 29. The last column gives the same date’s position in the 1994–2014 ranking.

The least common birthdays, 1969–1988

February 29 occurred in 5 of these 20 years (1972, 1976, 1980, 1984, 1988), 46,234 births in all and 9,247 per occurrence; by total it is #366 here as in 1994–2014, so it is set aside from the list above.

The weekend gap, year by year

Each year is measured against itself: Saturday and Sunday births per day as a percentage of Monday-to-Friday births per day in that same year. In 1969 the level was 88%; in 1988, 79%; by 2014, 64%. The years 1989–1993 are outside both files and are left blank.

Months, then and now

Births per day by month as an index where 100 is the window’s average day. September led in 1969–1988 at 107.2, and April was the quietest at 96.1. Each line is indexed to its own window, so they show shape.

Fixed-date holidays, then and now

Seven dates that fall on the same calendar day every year, as an index of that window’s average every-year date by share. A fixed date falls on each weekday about equally often across twenty years, The series records the moves.

Dates whose share rose most between the two windows

Each date’s share of its own year’s births, per 100,000, averaged over the twenty years of 1969–1988 and the twenty-one of 1994–2014. Because the two windows come from different compilations of federal records with five missing years between them, a move here is weaker evidence than the same move inside one file.

Dates whose share fell most

Did the calendar get less even?

Across the 365 dates that occur every year, the standard deviation of the per-date share was 11.82 per 100,000 in 1969–1988 and 14.15 in 1994–2014; the busiest date stood 1.38 times above the quietest then and 1.87 times later. On both measures the later calendar is less even. The weekend gap above is the largest single factor this series can see. Anything else is outside it.

Check how rare your own birthday is → · Change inside one file, 2000–2014 · Births by weekday