How often does February 29th happen?

February 29th occurs once every four years during a leap year, which is when an extra day is added to the calendar to keep it aligned with the Earth's orbit around the Sun. Leap years are typically those divisible by 4, but years divisible by 100 are not leap years unless they are also divisible by 400. This means that while most leap years happen every four years, there are exceptions that can affect the cycle.