why are there 365 days in a year?

At camp we are encouraged to Explore the Why. Me and my group want to discover why there are 365 1/4 days in a year? This happens because earth takes 365.25 days to go around the sun. The earth orbits the sun because suns gravity pulls the earth closer. There are extra days in some years ;and every 4 years there is a leap year to make up the 4 quarters.We were curious because we didn't know that the earth takes 365.25 days to go around the sun. This effected us because now we know more about earth. Rotate is how long it takes a planet to spin around orbit is how long it takes a planet to rotate around  the sun