three shows left syndication in 2013. Cable television Networks and programming blocks Two prominent nighttime-only cable and satellite channels currently operate in the United States: Nick at Nite, a collection of primarily reruns of older and some recent network sitcoms—as well as occasional prime time movie presentations—that airs over the channel space of Nickelodeon normally between 9:00 p.m. and 6:30 a.m. Eastern Time (, Nick at Nite’s start time is subtracted by 30 minutes or one hour on Saturdays depending on the week, and its end time is subtracted by one hour on weekends to accommodate regularly-scheduled extensions of Nickelodeon’s schedule, such as its Saturday block of first-run live-action series aimed at pre-teens and young teenagers, on those nights), and Adult Swim, a block of animated and a limited amount of live-action programming targeted toward older teenagers and young adults that shares space on the channel slot of Cartoon Network nightly from 8:00 p.m. to 6:00 a.m. Eastern Time. (In addition to reruns of sitcoms and—occasionally until the late 1990s—half-hour dramas, Nick at Nite also offered a limited amount of first-run original programming, mainly between 2005 and 2018.) As the number of cable channels expanded during the 1980s and 1990s, up until late into the latter decade, it was fairly common for two or more standalone networks to share space on a single channel (usually with one service occupying the daytime hours and the other occupying nighttime slots), a method used in particular by cable systems to account for limitations to headend infrastructures of the time period, which afforded a relatively limited number of channels that could be allocated to a single system’s lineup (an issue rectified by systematic headend upgrades that allowed for the implementation of digital cable service by the late 1990s). In such cases, cable system operators would typically switch between continuously-running channel feeds between dayparts. In its first six years of operation, Nickelodeon leased transponder airtime to offer The Movie Channel (from April 1979 to January 1980, as a part-time scrambled signal accessible only to subscribers of the premium service), the Alpha Repertory Television Service (ARTS) and its successor A&E (from April 1981 to February 1984 as ARTS, and until December 1984 as A&E) over its channel space during the network’s nighttime off-hours, each of which (with the exception of ARTS, which merged with film- and arts-oriented premium-turned-basic service The Entertainment Channel in February 1984 to