Is June 21 a rare birthday? Rank and weekday comparison

June 21 is relatively common in the historical U.S. birthday ranking. It ranks #124 overall and #11 within June, where #1 means most common. Its small difference from nearby dates of the same weekday changes direction when we change the comparison window.

There are 238,105 June 21 births in the selected 1994 through 2014 records: 0.278% of all recorded births, or about 1 in 360. This describes a historical birth-record sample, not the count of living people who share the date.

How does June 21 compare with June 20 and 22?

June 21 sits between its immediate neighbors in the combined baseline: below June 20 and above June 22. It is close to June 14, while June 28 and July 1 have higher totals.

The date occurred 21 times in the covered period, with 11,338.3 recorded births per occurrence. Month rank and overall rank answer different questions: the June guide compares only June dates; the rarest-birthday ranking compares dates across the year.

Those totals are useful context, but neighboring dates do not share a weekday in a particular year. The annual comparison accounts for that difference.

What happens when weekdays match?

In SSA data from 2000 through 2014, June 21 averaged 11,605.2 recorded births. Eligible dates one and two weeks before and after averaged 11,548.6. The pooled difference is +0.5%, with June 21 above its nearby mean in 9 of 15 years and below in 6.

Using only one-week neighbors gives -1.3%. Using only two-week neighbors gives +2.4%. The direction flips. A claim that June 21 runs consistently above or below nearby matching weekdays therefore depends on which neighbors we choose.

It does not change June 21's rank in the separate full-period ranking. A total-based rank and a local same-weekday difference measure different things.

Why were some comparison dates excluded?

The main comparison retains 58 eligible controls and excludes 2. The excluded dates are July 5 in 2004 and 2010, when that Monday was the standard federal observed date for Independence Day. The OPM observed-holiday rules supply the calendar rule, not a claim about hospital closures.

We average the eligible dates within each year first. A year with an exclusion still contributes one annual comparison. The weekday/weekend article gives the wider weekly context. Matching weekdays and screening holidays cannot remove every seasonal difference or explain individual birth timing.

Sources and calculations

We use U.S. daily births compiled by FiveThirtyEight: CDC/NCHS for 1994 through 1999 and SSA for 2000 through 2014, excluding overlap. Rank and share use the combined baseline; the yearly comparison stays within SSA alone.

The pooled percentage divides summed June 21 counts by summed annual control means. The analysis download preserves the individual counts, exclusions and alternate windows. Read the methodology for coverage limits, or check your own birthday. These records do not establish a solstice effect or a worldwide June 21 birth pattern.