Most United States AM radio stations are required by the Federal Communications Commission (FCC) to shut down, reduce power, or employ a directional antenna array at night in order to avoid interference with each other due to night-time only long-distance skywave propagation (sometimes loosely called ‘skip’). Those stations which shut down completely at night are often known as "daytimers". Similar regulations are in force for Canadian stations, administered by Industry Canada; however, daytimers no longer exist in Canada, the last station having signed off in 2013, after migrating to the FM band.