The Discovery Channel began broadcasting on June 17, 1985. It was initially available to 156,000 households and broadcast for 12 hours each day between 3 p. m. and 3 a. m. About 75 percent of its program content had never been broadcast on U. S. television before. In its early years, the channel's focus centered on educational programming in the form of cultural and wildlife documentaries, and science and historical specials. It also broadcast some Soviet programming during this time, including the news program Vremya. In 1988, the channel premiered the nightly program World Monitor (produced by The Christian Science Monitor). In 1988, The Discovery Channel debuted an annual programming stunt called Shark Week, the week-long event eventually gained in popularity starting in the 1990s and continues to be shown each summer on the channel to this day. By 1990, the channel was available in over 50 million households.