Effects of time zones on North American broadcasting Effects of time zones on North American broadcasting The scheduling of television programming in North America (namely the United States, Canada, and Mexico) must cope with different time zones. The United States (excluding territories) has six time zones (Hawaii–Aleutian, Alaska, Pacific, Mountain, Central and Eastern), with further variation in the observance of daylight saving time. Canada also has six time zones (Pacific, Mountain, Central, Eastern, Atlantic and Newfoundland). Mexico has four time zones (Pacific, Mountain, Central, and Eastern). This requires broadcast and pay television networks in each country to shift programs in time to show them in different regions. Canadian
Prime Time Access Rule hour of prime time (7:00–8:00 p.m. Eastern Time and Pacific Time, 6:00–7:00 p.m. Central, Mountain, Alaska and Hawaii–Aleutian Time) as the "prime access hour". By the early 1980s, the PTAR had introduced a policy amendment prohibiting stations in the 50 television markets with the highest prime time viewership from broadcasting more than three hours of network programming during the four-hour "prime time" block. Stations had to find original programming to fill during the "prime time" fraction. However, the rule exempted certain types of programming, such as overruns of live sports events, special news, documentary and children's programming, and certain sports