For reference time zones adopted special standard time, abbreviated UTC (Coordinated Universal Time).This time on the zero meridian, it does not change between summer and winter, so the calculation of the local time, you need to pay attention to it.
UTC is based on the international atomic time, which is calculated according to the testimony of more than 200 atomic clocks in research laboratories around the world.The offset time zones east of UTC is recorded as UTC + 1, UTC + 2, etc.to UTC + 14, the shift to the west respectively UTC-1, UTC-2, etc.UTC-10.Moscow time from March 27, 2011 corresponds to UTC + 4.
concept of time zone can sometimes be supplemented by the coincidence of the dates.That is, the UTC UTC + 14 and
-10 will be different time zones, even though the time of day in which the same.
theory is based on the time it passes through a specific meridian and time zones must be the same.In fact, to save the local time in certain administrative or natural one, time zones are of different length.Sometimes administrative-territorial regions do not impose the same local time because of their enormous size.For example, the Republic of Sakha (Yakutia) in Russia is divided into three time zones.Some time zones that should exist in theory to match the natural time just disappear between adjacent because of the great length of the region from west to east.
through the territory of many countries goes through several common time zones.For example, in Russia there are eleven in Canada - six in the United States - five, in Greenland - four.Mexico and Australia are living in three time zones, and Kazakhstan, and Brazil in two.China is located in the five standard time zones, but the whole of its territory is a single time.
concepts of "local time" and "time zone" are meaningless in the South and the North Pole, as meridians in these regions converge at one point.It is believed that while the poles similar to the worldwide.However, at the Amundsen-Scott Station at the South Pole made while in New Zealand.
have not yet been introduced time zones, every city used its own local solar time corresponding longitude.When they began to develop means of communication require a more precise system of compliance.In the late 70-ies of the XIX century in North America, it introduced a system of time zones used until now.In Russia, began to apply the time zone only after the 1917 revolution.