Eventually, the calendar we all know was adopted by Pope Gregory XIII in 1582, and it's changed little since then — not that the system is flawless. February gets a leap year once every four ...

February is packed with interesting observances, but one that stands out is Leap Day—and the Leap Year that makes it possible ...

What is a leap year? Generally we define a year as 365 days, but a full orbit of the sun actually takes around 365.25 days. This means every four years, we add an extra day to the calendar ...

Eventually, the calendar we all know was adopted by Pope Gregory XIII in 1582, and it's changed little since then — not that the system is flawless. February gets a leap year once every four ...