Question

why do leap years have 366 days

Answer 1

February 29 is a date that usually occurs every four years, and is called leap day. This day is added to the calendar in leap years as a corrective measure, because the Earth does not orbit the sun in precisely 365 days.

Answer 2

leap year comes in every 4yrs 1 normal year is 365 1/4 days so we count all the 1/4 days in the 4th yr