How long exactly is a year?

365 days 5 hours 49 minutes and 15.974 seconds and so yes this epic journy around the sun measures 548,018,150 miles (938,886,400km)and takes exactly 365.25 days, which gives us the calender year of 365 days.To make up the extra 0.24 days we add a leap year to our calander in the end of February in every fourth year,which is called the leap year,_ and then we have to knock off a leap year every four centuries