Quote:

Originally Posted by

**Dobagoh**
This is false.

People are more likely to be born during the spring and fall months (humans have "breeding seasons" during the summer and winter seasons, so that babies are more likely to be born when food is plentiful. The probability of 2 people having the same birthday, is thus dependent on when they were born, and is not equal to 1/365.

The problem assumes a uniform distribution.

Assuming the uniform distribution, the probability of a mutual birthday (ignoring February 29th) P(n) is :

P(n) = 1 - (n!(365-choose-n))/(365^n)

where

365-choose-n = (365!)/((n!)((365-n)!))

By the pigeonhole principle, this probability is 1 if there are 366 or more people in the room.