That is considered to be a sidereal year and slightly longer than a calendar year. That 5 hours, 48 minutes and 56 seconds is extra time and needs to be used. Therefore, it is used on a Leap Day.

This ‘sidereal’ year is slightly longer than the calendar year, and that extra 5 hours 48 minutes and 56 seconds needs to be accounted for somehow.” according to the Smithsonian Institute.

What would happen if we didn't have leap years? That extra time known as a "sidereal" year must be accounted for somehow, the magazine says. Otherwise, seasons could be impacted.

Because this "sidereal" year is slightly longer than the common year, the hours need to be accounted for − leading to the need for leap years with an extra day.

Because this "sidereal" year is slightly longer than the common year, the hours need to be accounted for − leading to the need for leap years with an extra day.

Because this "sidereal" year is slightly longer than the common year, the hours need to be accounted for − leading to the need for leap years with an extra day.

According to the Smithsonian: This “sidereal” year is slightly longer than the calendar year, and that extra 5 hours 48 minutes, and 56 seconds needs to be accounted for somehow.

It's not every year that you see February 29 on the calendar -- and it's not technically every four years either. Thursday is officially leap day. For some, its birthdate, or a day for special ...

Because this "sidereal" year is slightly longer than the common year, the hours need to be accounted for − leading to the need for leap years with an extra day.

It’s not every year you see February 29 on the calendar — and it’s not technically every four years either.