Today it is the birthday of Edmund Kean, the famous English actor. I posted his picture not because I am a fan of early 19th Century Shakespearean theater but because I fondly recall the Broadway musical Kean from the 1960's. (What, you don't remember that musical? Most people don't. That's OK.)
Yesteday it was composer John Barry's birthday; movie fans will be familiar with his many soundtrack scores. Tomorrow is Art Garfunkel's birthday. (You remember Garfunkel; Paul Simon -- not the politician, the singer -- was his sidekick for a while.)
Basically, I post a birthday for someone whose life or work has some interest to me. I posted Monica Bellucci's birthday, for example, not because she is insanely beautiful but because of her performances in the Matrix movies and in one of my favorite Bruce Willis movies, Tears of the Sun. Captain James Cook appeared because he was one of the greatest explorers who ever lived. Milton Nascimento creates great music.
The two online sources I use most frequently to locate interesting birth dates are HistoryOrb.com and Wikipedia. Unfortunately, they both suffer from the generic problem of all such lists: they overemphasize Dead White Males. Women and non-whites are in the definite minority of such lists online, and some lists are just "celebrity heavy."
If you know of any more extensive or inclusive online sources for birthday I should check out, please post a comment below or email me at firstname.lastname@example.org. I'm especially interested in inventors, scientists, and explorers. Thanks!