People are posting about how there are some upticks in births corresponding to popular times of conception, like Valentine's day and Christmas. That's all true, but i don't think that the human gestation period is so consistent that this would account for a sudden surge in births on one day, compared to just a few days previously. The babies conceived on a given day are not all born on the same day.
Part of the explanation lies simply in the nature of randomness.
Professors teaching statistics sometimes give the following assignment: toss a coin 100 times, and record the sequence of heads and tails you get.
The next class period, the professor collects the papers, and just by glancing at them can call out which students really took the time to toss the coin 100 times, and which students just fabricated a "random" sequence of H's and T's while figuring nobody would be able to tell the difference.
As it turns out, in 100 tosses of a fair coin, there is a very high probability of a run of length 7: seven heads in a row or seven tails in a row. Runs of length 5 or 6 are of course even more common. But most "cheaters" will probably avoid more than 4 in a row, misunderstanding how randomness works.
And likewise, every now and then, there will be a surge of births in a short time period, just due to chance.
