This phrase is best uttered from an open doorway, as the dusk gathers around you and the lights of the town start twinkling on. In the spring and summer, it can be accompanied by the sound of crickets or frogs.
"Kids, it's getting dark. Time to come in!"
I think I'm going to love this trampoline thing. Despite a few House Rules that need to be ironed out (how many can be on at one time, that sort of thing), and a couple of bumps and bruises, the kids were out there with their friends all afternoon until it was literally so dark I almost couldn't see them.