where did summer go?

So my oldest 2 children go back to school on Wednesday. I can not believe that the summer is over. It seems that we just went to the last day of school picnic with E. I guess it has been 3 months I just want to know why the 3 months of summer go so fast and the 3 months of true winter seem to crawl by. That is someones idea of a joke I'm sure.