We call that a tropical year, and that's what we base our calendar on, at least here in the west.

我们称之为热带年，这就是我们日历的基础，至少在西方是这样。

And since a tropical year is a tad longer than 365 days, Julius added a leap day every four years, except they inserted it after February 23, right in the middle of the month.

但，因为，回归年并不是正好365天，而是365.242天。Julius每隔4年，加一天，除了要加在2月23日的后面，还要在2月的中间日。