Probability of 3 people having birthday in March If there are 3 people, what’s the probability that all 3 are born in March? None of them are born in a leap year and there are 31 days in March.

If we assume that all days are equally likely to be a person's birthday, and that the three people's birthdays are independent events, then the probability is just the product of the probability of the individual events: $\left(\frac{31}{365}\right)^3$.

Empirically, these assumptions could both likely be false.