What has 366.25 days?

Answer 1

A year with 366.25 days refers to the average length of a year in the Gregorian calendar when accounting for leap years. Typically, a standard year has 365 days, but every four years, an extra day is added to February, creating a leap year with 366 days. The average of 366.25 days arises from the inclusion of leap years and the adjustment made for the fact that the Earth takes approximately 365.2425 days to orbit the Sun.