Do you ever feel like you're always running into people with your birthday? It might not be you; it might be the date that you were born. Matt Stiles' birthday heat map gives us a picture of which birthdays are the most and least common in the United States.
Stiles used a table that ranks birthdays for people born between 1973 and 1999, which you can view at the New York Times. The darker colors indicate the date has a lower-numbered birthday rank and the lighter colors a higher-numbered birthday rank. February 29th and December 25th were ranked 366th and 365th in rank, respectively, while September 16th was the most common birthday. One thing is clear from Stiles' visualization of the data: card-shopping season has just begun.
Also check out the Birthday Paradox, which examines the question: What is the likelihood that, in a given group of people, two will share the same birthday?
Edit: Based on this chart, Lane Harrison has created an interactive chart with both the birthdate ranks and the approximate conception ranks, giving us a picture of the US' amorous winter months. And what is going on in early April that makes us want to get it on?