Day to night

 I masked out the sky on the Castle and i also masked out the ground on the moon. I also had to copy and paste the moon a little higher because the castle was blocking it. I used curves, levels, and Hue/Saturation. I also used the burn tool to make the grasss and castle a little darker. I made a copy of the trees and flipped it upside down and i went down on the opacity to make a shadow. I also used the burn tool on the shadow.