A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. It is convenient for areas in close commercial or other communication to keep the same time, so time zones tend to follow the boundaries of countries and their subdivisions.
Most of the time zones on land are offset from Coordinated Universal Time (UTC) by a whole number of hours (UTC−12 to UTC+14), but a few are offset by 30 or 45 minutes (for example: Nepal Standard Time, NPT). Some higher latitude countries use daylight saving time for part of the year, typically by changing clocks by an hour. Many land time zones are skewed toward the west of the corresponding nautical time zones. This also creates a permanent daylight saving time effect.
Human geography is one of the two major sub-fields of the discipline of geography. Human geography is a branch of the social sciences that studies the world, its people, communities and cultures with an emphasis on relations of and across space and place. Human geography differs from physical geography mainly in that it has a greater focus on studying human activities and is more receptive to qualitative research methodologies. As a discipline, human geography is particularly diverse with respect to its methods and theoretical approaches to study.
Geographical knowledge, both physical and social, has a long history. In the history of geography, geographers have often recorded and described features of the Earth that might now be considered the remit of human, rather than physical, geographers. For example Hecataeus of Miletus, a geographer and historian in ancient Greece, described inhabitants of the ancient world as well as physical features.
The Mountain Time Zone of North America keeps time by subtracting seven hours from Greenwich Mean Time, during the shortest days of autumn and winter (UTC−7), and by subtracting six hours during daylight saving time in the spring, summer, and early autumn (UTC−6). The clock time in this zone is based on the mean solar time at the 105th meridian west of the Greenwich Observatory. In the United States, the exact specification for the location of time zones and the dividing lines between zones is set forth in the Code of Federal Regulations at 49 CFR 71.
In the United States and Canada, this time zone is generically called Mountain Time (MT). Specifically, it is Mountain Standard Time (MST) when observing standard time (fall and winter), and Mountain Daylight Time (MDT) when observing daylight saving time (spring and summer). The term refers to the fact that the Rocky Mountains, which range from northwestern Canada to the US state of New Mexico, are located almost entirely in the time zone. In Mexico, this time zone is known as the Pacific Zone.
The Wake Island Time Zone observes standard time by adding twelve hours to Coordinated Universal Time (UTC+12). The clock time in this zone is based on the mean solar time of the 180th degree meridian east of the Greenwich Observatory.
The zone includes the U.S. territory of Wake Island and is two hours ahead of Chamorro Time Zone, 23 hours ahead of Samoa Time Zone, and 24 hours ahead of Howland and Baker Islands.
The Samoa Time Zone observes standard time by subtracting eleven hours from Coordinated Universal Time (UTC-11). The clock time in this zone is based on the mean solar time of the 165th meridian west of the Greenwich Observatory.
The zone includes the U.S. territory of American Samoa, as well as the Midway Islands and the uninhabited islands of Jarvis, Palmyra, and Kingman Reef.