International Meridian Conference
On 11 October 1883, a convention of railroad executives met in Chicago and agreed to the implementation of five time zones in North America, using as a basis Greenwich Mean Time. Before the invitations to the Washington conference were sent out on December 1, the joint efforts of Abbe, Fleming and William Frederick Allen, Secretary of the US railways' "General Time Convention" and Managing Editor of the "Travellers' Official Guide to the Railways", had brought the US railway companies to an agreement which led to standard railway time being introduced at noon on 18 November 1883 across the nation. Although this was not legally established until 1918, there was thus a strong sense of "fait accompli" that preceded the Washington conference, although setting local times was not part of the remit of the conference.
Effects of time zones on North American broadcasting
Local programming such as locally produced newscasts are not typically affected as many stations air their morning newscast at 4:00, 4:30, 5:00 or 5:30 a.m., and their early evening newscasts at 5:00 and/or 6:00 p.m.; however, the late evening newscast is affected due to the differences in time between time zones, meaning that if the late local news starts at 10:00 p.m. Central time on one network station, an affiliate of the same network in the Eastern Time Zone airs its newscast at 11:00 p.m.; network evening newscasts on CBS, ABC, and NBC are affected since they are usually scheduled to air at 6:30 p.m. Eastern Time (barring preemption due to network sports coverage or at the discretion of the local station, breaking news or severe weather coverage) in order to sync up with its simultaneous broadcast in the Central Time Zone. Midday newscasts are not necessarily affected, depending on whether the station's affiliated network schedules their daytime lineup simultaneously in the Eastern and Central Time Zones (as with ABC and CBS) or just to the Eastern Time Zone first (as with NBC). The late night program lineups on ABC, CBS, NBC and Fox are also similarly timeshifted, airing a half-hour later (after a newscast or syndicated programming if the station does not run news programming) but are shifted due to the time zone differences (a bigger issue with first-run late night programs that air after 12:30 a.m. Eastern Time since the later start time may subject these programs to a potentially decreased audience). Many Fox, CW and MyNetworkTV affiliates, and some independent stations carry a prime time newscast that is similarly affected by the timeshifting of the prime time schedule, meaning that if said late evening newscast starts at 9:00 p.m. Mountain Time on one network station, an affiliate of the same network in the Pacific time zone would air its news at 10:00 p.m.