In my experience, it was always best for all concerned to say (for example), "On Saturdays you have possession of the girls from XX a.m. to XX p.m." That way you can plan your life and he doesn't have to spend his time trying to run you down. Our unspoken rule was, "Don't call me unless someone is bleeding enough to need a tourniquet. Go have fun with your kids." You deserve a day of peace and quiet after all week of single parenting.