Years

thumb|alt=see caption|upright=1.5|An animation of the inner Solar System planets' orbit around the Sun. The duration of the year is the time taken to go around the Sun. A year is a unit of time based on how long it takes the Earth to orbit the Sun. In scientific use, the tropical year (approximately 365 solar days, 5 hours, 48 minutes, 45 seconds) and the sidereal year (about 20 minutes longer) are more exact. The modern calendar year, as reckoned according to the Gregorian calendar, approximates the tropical year by using a system of leap years.

year that does not exist in the Anno Domini / Common Era year-numbering system