Thursday is Leap Day—when we add an extra day to the month of February.
So why do we do it? Dr. Bob Craddock of the Smithsonian Institute says a year is actually 365 days, 5 hours, 48 minutes and 56 seconds—which means eventually it would have an impact.
“If we didn’t adjust for the additional time somehow, then our calendar year is going to start earlier than what we call the sidereal year. Our dates and events are going to start slipping forward,” Craddock said.
Craddock says Leap Years usually occur every four years, however there’s also an exception to that rule.
“If you’re doing the math the 5 hours, 48 minutes and 56 seconds isn’t exactly six hours. So what we’re doing is actually adding time to our calendar every time we have a Leap Day,” Craddock said. “So somehow or another we have to address the extra few minutes we add to the calendar every four years.”
That means we skip Leap Day every 100 years, unless they are divisible by 400. So the next Leap Day we’ll skip will be in 2100.
