There are 18 starting positions in a baseball game. The odds that any two starting players share a birthday is slightly less than 1 in 6. The odds of two pitchers sharing a birthday is about a little more than 1 in 55. Multiply that by 162 games per team per season... im surprised they went this long without starting pitchers sharing a birthday.

FlyingLizardOfDoom: There are 18 starting positions in a baseball game. The odds that any two starting players share a birthday is slightly less than 1 in 6. The odds of two pitchers sharing a birthday is about a little more than 1 in 55. Multiply that by 162 games per team per season... im surprised they went this long without starting pitchers sharing a birthday.

I don't think it was just sharing their birthday, but also pitching ON their birthday.

This isn't an original thought, but Homer really is such an unfortunate name for a guy who grew up to be a pitcher. It's the exact opposide of Tim Duncan.

FlyingLizardOfDoom: There are 18 starting positions in a baseball game. The odds that any two starting players share a birthday is slightly less than 1 in 6. The odds of two pitchers sharing a birthday is about a little more than 1 in 55. Multiply that by 162 games per team per season... im surprised they went this long without starting pitchers sharing a birthday.

but how often do they play a game on their birth date? especially if both guys play a position that only plays every fifth game. the two guys could share the same birthday of jan 15th. doubt they will ever play a game against each other on that date.

I thought about that after I posted. Restating the odds to account for that, it would be approx. 162/365*55 or 0.8%, approximately once in 124 years or so. Still slightly overdue.

FreakinB: This isn't an original thought, but Homer really is such an unfortunate name for a guy who grew up to be a pitcher. It's the exact opposide of Tim Duncan.

Not as bad as Grant Balfour.

OK, I was at that game and it was my birthday too. So, that makes it really spooky.

Chakro: OK, I was at that game and it was my birthday too. So, that makes it really spooky.

And they didn't have you sign the baseballs, too??? Shameful!

/Happy birthday.

chimp_ninja: Odds per game:
(1 in 365.25 that Starting Pitcher A's birthday is today) * (1 in 365.25 that Starting Pitcher B's birthday is today) = ~1 in 133,407 games.

No.

uber humper: I was trying to figure does it matter that the season is only ~half a year. In that half of the pitchers would never have a chance of that happening?

The odds of it being one random pitcher's birthday on any given date do not vary because of the length of the season, assuming that the overall range of birth dates is more or less evenly distributed between days of the year. Even if certain time frames did contain more birthdays I'd think that over the time span & number of pitchers involved, the effect on the answer would be minimal (small fractions of a percentage point).

mohron: Treygreen13: FreakinB: This isn't an original thought, but Homer really is such an unfortunate name for a guy who grew up to be a pitcher. It's the exact opposide of Tim Duncan.

Not as bad as Grant Balfour.

Or Doug Fister.

Or pro golfer Bogey McBogerson

tedeb: Hoopy Frood:The range of birth dates isn't evenly distributed. If you start in the six-year-olds' league and you have a birthday right after the previous cutoff date, being eight or ten months older makes a big difference. You'll probably be bigger and more athletic than the other kids. You're more likely to get more attention from coaches and play more. The next year, not only are you still bigger and more athletic than the other kids, but you benefit from having been bigger and more athletic the previous year. If you have a "late" birthday, just the opposite. Unless you want it more and bust your butt, you're more likely to quit sooner.

+1 to you. not even close to evenly distributed:
Link

Fair enough, let's try something using the data that tedeb provided. For simplicity's sake, we will assume a season running from April 1st to October 31st; this includes some playoff games but ignores a handful of official games played outside that range each season. This equates to roughly 58% of the calendar year (58.333% if you want to be precise).

From the data in the linked table, a total of 3243 players were born on dates within the baseball season; 2304 were born on dates outside of the season. That equates to...roughly 58% of big leaguers (58.464% to be precise). In other words, while a few months are heavier on birth dates, overall it's equally likely that a major leaguer will celebrate his birthday during the season as outside of it (slightly more likely, to be precise). This is not perfect as these numbers include position players as well as pitchers, but it's what we have to work with (and I think it's safe to assume that over time, any particular position will have a similar spread throughout the calendar year).

Again, the overall effect of birth month distribution is negligible in determining the likelihood of two random major league starting pitchers being born on the date when they face each other. It would have the effect of making it slightly more likely to occur on a date in August vs. a date in May, but not overall.

Hoopy Frood: The next year, not only are you still bigger and more athletic than the other kids, but you benefit from having been bigger and more athletic the previous year. If you have a "late" birthday, just the opposite. Unless you want it more and bust your butt, you're more likely to quit sooner.

Must you also be scrappy?

/more likely you develop faster than other kids your age or are extraordinarily gifted, not "you want it more"

Treefingers: Okay, what if there are a disproportionate number of players born on certain months within the season over others? Say, baseball is a sport that draws players born in certain months. Wouldn't that alter your stats a bit? You'd need a list of the number of players born by month of the season to even mathify it.

Farking insomnia.

It might alter it a bit, but not by a noticeable amount over the sample size we're talking about. It only has a significant effect on the results if you're solving for a given date or month, not for a random date within the season; in the latter case, months which average fewer birthdays are mostly offset by the months which average more.

All that being said, I'm much stronger with logic than I am with math, and I don't deny the possibility that I'm overlooking something on the math side.