Amitabh Chandra of Harvard University provided the data for a New York Times article back in 2006 based on babies born in the United States on dates between 1973 and 1999.

The data (visualized on the headmap below) shows Sept. 16 was most common with Feb. 29 (only in a leap year) obviously the least common.

Data source: NYTimes.com, Amitabh Chandra, Harvard University.

For more check How Common Is Your Birthday – Pt 2.

(via broadsheet)