What are the chances your Grandma June was born in June? Or that your Uncle Patrick was born on St. Patrick’s Day? Can you say with reasonable certainty that your Great-Aunt Valerie was born in February?

Baby name popularity changes from year to year and from state to state. Is it possible that it also varies based on the month or even day of the year when a baby is born?

I wanted to find out. Unfortunately, while the Social Security Administration releases a list of the most popular baby names every year, the data doesn’t link names to birthdates—not at birth, it doesn’t. When you die—that’s a different story. After you breathe your last, your name is added to the Social Security Death Index, which includes your birthdate.

Using this data set, we can get a sense of how many people born on a specific day of the year have a given name. Consider the names Patrick and Patricia—and notice the spike on March 17:

Of course, because my data set only includes dead people, it skews old. People of all ages die constantly, so there is some representation from recent years, but the majority of the people in this data set were born between 1900 and 1950. (And the data set only includes Americans who had Social Security numbers, which were not issued universally during this period.) The charts above, and all charts in this graph, therefore have more to say about the residents of your local retirement home than your child’s kindergarten.

Still, this data set illuminates some basic trends in seasonal names, some of which we might expect to persist into our own time. Before I started this research, I thought there was a chance that people might actually avoid giving their baby a seasonally appropriate name. That did not turn out to be the case. The number of people in my sample who thought it a little too on the nose to name a June baby June were far outnumbered by those who thought it just right. Almost half of all babies named June were born in the eponymous month:

There are plenty of less obvious patterns as well. John spikes on June 24, which several branches of Christianity, including Catholics, celebrate as the feast day of John the Baptist:

This phenomenon is one we might expect to be less pronounced among babies born more recently, if you presume that the tradition of naming a child after a saint’s day or feast day is an Old World convention that’s waned over time. In the chart above, you can also see the two largest single-day dips in John’s popularity are on Feb. 22 and March 19. These days see a spike in the names George (President Washington was born on the 22^nd) and Joseph (St. Joseph’s Day is March 19).

Below is a calendar showing the most distinct name for both genders for each month. The calendar does not show the most popular names for each month—that would have yielded the same few names throughout the whole year (mainly John and Mary). These are the most distinct names—the names most common compared with their frequency in other months. In creating the calendar, I included only the top 100 names for each month, in order to sort for names that are both popular and heavily concentrated in one month. It’s an arbitrary cutoff, but otherwise, obscure religious names like Inocencio and Hipolito would have dominated the chart. Again, this data is skewed toward older naming patterns. But it’s likely that May would still dominate May today and that Nicholas might hold his ground in December.

Religion lurks behind most of these names. Esther spikes around the time of Easter and Purim, while names like Andrew, Peter, and Josephine all spike around their saint’s days (St. Joseph for Josephine).

Again, none of these seasonal trends is constant over time. For most names, it appears the variation is not as extreme as it once was. Looking at the name June from 1900 to 1985, we see that the proportion of Junes born in June still stands well above the roughly one-twelfth we would expect if there were no seasonal variation. But the popularity of naming a baby June in June has slipped over time:

Naming habits evolve, but they’re very slow to disappear. Looking just at the years 1975 to 2010, there are still more Valeries born on Feb.14 than any day of the year; more Noels, Christinas, and Christians on Dec. 25; more Junes on June 1; and more Patricks on March 17.

If you happen to meet someone named Vladimir on Tuesday, make sure to wish him well. Tuesday is July 15, feast day for Vladimir the Great, and—historically speaking—there’s a decent chance it’s the person’s birthday.