Leap Year celebrations
February 29 is added to the calendar in leap years as a corrective measure, because the earth does not orbit around the sun in precisely 365 days.
Of course if you're born on February 29th you only get to celebrate your brithday every four years.
Like Linda Davies from Hinderclay in Suffolk and her mother, Christine Harold, who are a very sprightly 13 and 20 today (or rather 52 and 80!)