The average year is, in fact, 365.242 days long – just so long as you’re not talking about the sidereal year. So what’s that? Simply put, a sidereal year – it’s pronounced sy-dear-ee-al ...

Leap years account for the inaccurate measure of time on the 365-day calendar. Technically it takes 365.242190 days for the Earth to orbit the Sun, which is known as the "sidereal year," according to ...

Slightly less than the 24 hours of a solar day (23 hours, 56 minutes, 4.1 seconds). Used in astronomy, sidereal means "when a star crosses the meridian" (the meridian is an imaginary circle around ...