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
Effectively, the East, Mountain and West network feeds allow prime time on broadcast television networks to end at 10:00 p.m. Central and Mountain and 11:00 p.m. Eastern and Pacific. When it first expanded its programming into prime time in April 1987, Fox became the first major broadcast network in the U.S. to offer a "common prime" schedule; this type of scheduling subtracts an hour from the prime time schedule, reducing it to two hours on Monday through Saturdays and three hours on Sundays – ending evening network programming earlier than NBC, CBS and ABC did – and continue to do (Fox did expand its Sunday primetime schedule into the 10:00 p.m. timeslot in September 1987, before giving back that hour to its stations in September 1993). The WB and UPN followed the "common prime" scheduling model when they both launched in January 1995; the replacements for those networks, The CW and the MyNetworkTV program service, similarly used that model upon their launches in September 2006.