text: It depends on the persons situation.\n\nIf the person is at school or any other situation where they are with people of the same age, the odds of anyone you meet sharing birthdate is 1/365.  Therefore - in a class of 36 on their first meeting (ie. start of school) roughly there's a 10% chance of meeting someone with the same birthdate.\n\nIn general - someone you meet is going to be between 1-80 years old and born on 1/365.25 (incorporating leap-years) days.\n\nSo say roughly 1/30000.\n\nObviously - if you go to an area with a high number of retired people whilst you are young - the odds are drastically reduced - and vice versa.