Do you know how many days there are in one year?  Most years have 365 days.  Some years have 366 days. 

      A year is the time it takes for the earth to go around the sun.  It takes a little more than 365 days.  It takes 365 days, five hours, 48 minutes, and 45 seconds.  In each year of 365 days, there is time that doesn't get used.  The extra is five hours, 48 minutes and 45 seconds is saved.  Every four years the exta time is put together.  It makes an extra day.  The extra day is February 29.  In most years, February has 28 days.  But once every four years, it has 29 days.  A year with an extra day is a leap year.