The period of time during which Earth completes a single revolution around the sun, consisting of 365 days, 5 hours, 49 minutes, and 12 seconds of mean solar time. In the Gregorian calendar the year begins on January 1 and ends on December 31 and is divided into 12 months, 52 weeks, and 365 or 366 days, A period of approximately the duration of a calendar year, Age, especially old age