2016 is a leap year, when a Leap Day is added as 29th February. It was added by the Roman Emperor Caesar Augustus. It is needed every 4 years to keep our calendar in alignment with the Earth’s revolution around the Sun. It takes exactly 365.2442 days for a complete orbit of the earth around the sun.
This extra day makes the year 366 days long instead of 365, there will be a February 29 2016.
Tradition says that in a Leap Year a woman can propose to a man. St Patrick supposedly gave women the chance to propose to their suitor every Leap Year, after St Bridget had complained that some women were having to wait too long for their men to propose. Unfortunately research shows that it usually ends in failure.