Why does a year have 365 days but calculates to 364 days?

There is actually 364.something amount of days in an actual year and there is 365 days in a leap year A year is 365.24 days. This is calculated by the stars (sidereal year), we use a leap year to even out the minor discrepancies (2000 was not a leap year), but we are slightly off the sidereal year most of the time. The leap year has 366 days.