Earth & Conservation

Why Do We Have Leap Years?

Every four years, we get an extra day in February. Who decided this, and what's the point?

Sources:
http://www.slate.com/blogs/bad_astronomy/2014/01/01/new_year_2014_how_astronomers_define_the_year.html
http://www.public.asu.edu/~mjwhite/Sidereal%20and%20tropical%20years.pdf
http://www.astronomynotes.com/nakedeye/s7.htm
http://blogs.discovermagazine.com/badastronomy/2012/02/29/why-we-have-leap-days-2/#.Vj_Bf-nXGkM