Prime time starts at 7:00 p.m. on the east and west coasts, and an hour earlier in the Central and Mountain time zones. During this hour, networks generally warm up the evening with comfortable, familiar programming such as long-running game shows, entertainment magazine programs and the most popular syndicated sitcoms. On cable, re-runs usually fill the spot, with exceptions including sports channels, news channels and channels geared towards children, which may run their top new shows in this slot, before the parents take over the TV.
During the regular programming season, prime time is in full force at 8:00 p.m. on the east and west costs, 7:00 p.m. Central and Mountain. This hour is traditionally family hour, with programming that is suitable for all ages, including family sitcoms and medical dramas. Very intense or violent dramas and comedies with more of an adult demographic don't run during this hour, as kids in many American households are still up and frequently watching.
The 9:00 p.m. hour in the east and west coasts, 8:00 p.m. Central and Mountain, is the most-watched hour of television in the whole day. This hour is often reserved for the networks' top shows, and commands the most advertising dollars. While on network TV programming is in the PG to PG-13 range, shows are usually more adult in nature, and dramas and adult-geared sitcoms commonly fill the 9:00 p.m. spot. On cable, the programming is usually geared toward adults by this hour, often giving network TV heavier competition.
By the 10:00 p.m. hour, it's expected that the audience are adults, and the children have gone to bed. This gives even network TV more leeway, and programming at this hour can be more intense, with a higher level of violence, sex and adult language. On cable this is especially true, with programs that can equal, or nearly equal, an R rating for film. Cable's freedom to show more makes this a highly competitive time slot, with some networks switching to an early news broadcast.