February 29 is a date that only occurs once every four years, and is called leap day. This day is added to the calendar in leap years as a corrective measure, because the earth does not orbit around the sun in precisely 365.000 days. The chance of being born on leap year day is about 1 in 1,500, there are about 4 million people worldwide with February 29 as there birthday.
This is the algorithm that I used to determine if a given year is a leap year or not. I’m not sure where I got it from but it comes in handy when creating calendar applications.
if (year % 4 == 0) && ((year % 100 != 0) or (year % 400 == 0)) then leap else no_leap