An "Astronomy Night at the Spicer House" Presentation

The year 2020 has 366 days in it, thanks to February. Why does February have 29 days this year, but 28 on any other year? Why don't we make February 30 days and take away a day from two months that have 31 days instead?

Leap over to the Spicer House for a presentation that entails how the stars have shaped our calendar and why we add a day to February once every four years.