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.
Quintana Roo
On February 1, 2015, Quintana Roo officially adopted a new time zone, Southeastern, which is five hours behind Coordinated Universal Time (). Quintana Roo does not observe daylight saving time, so Southeastern Time is constant throughout the year (that is, it does not shift forward in the spring and back in the fall). Southeastern Time (ST) is the same as Eastern Standard Time (EST) and Central Daylight Time (CDT). This means that in the winter, Quintana Roo has the same time as regions observing EST, such as the eastern U.S., eastern Canada, Cuba, and Jamaica; and in the summer, Quintana Roo has the same time as regions observing CDT, such as central Mexico.