A time zone map is formed by the sum of all those parts of the earth’s surface, which are in the same state-controlled single time and the same date. This is the time zone to time zone associated time. The ideal time zone is a closed area, which also includes the relevant parts of the sea, and is shaped like a Kugelzweiecks, extending from pole to pole. Of these, the soft real time zones considerably.
Ideal and actual time zones
If we divide the earth into 24 equal ball exactly two vertex, created ideal 24 time zones. These extend across each 7 ½ degrees of longitude on either side of the reference longitude, which is ideally an integral multiple of 15 ° with respect to the internationally agreed the prime meridian. This has the following advantages:
The time zone is different to the zone boundaries only ± ½ hour from the mean solar time.
The time difference between the adjacent time zone is ± 1 hour.
Most states have chosen one of these 24 time zones as the statutory time (or more time zones in states with large east-west extension). The actual time zone is the sum of all states or parts with the same time zone and from selected areas of the oceans, which are always part of an ideal time zone map.
Colloquially, the term time zone can only be meant the territory of a state, rather than the area be designated as belonging to a time zone. Further confusion arises when the terms are time zone and time zone used as synonyms.
Some states do not use any of the 24 “ideal” time zones, which differ by an hour of each other. You choose a time in between, thus creating a ending on their southern and northern boundary time zone (eg India).
States with large east-west extension usually have multiple time zones (for example, U.S. and Russia). They divide their territory more or less in line with the “ideal” time zones. It can be made double or multiple broad national time zones (as in Russia), or in the state is only a single time zone is being used (in the People’s Republic of China).
The time zones are relative to universal coordinated universal time (UTC, Universal Time Coordinated), such as UTC +1 h (Central European Time CET) or UTC-3: 30h (Newfoundland Standard Time). Because the language is not always clear, a time zone is UTC ± x sometimes referred to as a time zone.
In some countries, in addition, about half a year between normal zone time (standard time, standard time, English Standard Time) and DST (summer time in English, Daylight Saving Time) on the menu.
The date changes every time zone, if it is midnight (24 world clock / 00 clock) there, or at the date line (change between the time zones to UTC +12 h or 12 h UTC). Thus, a time zone characterized also by the same valid date.
Occasionally there are changes, such as the shifts in Russia by the 2011 abolition was the winter time.
The legal times (time zones, including: standard times or normal times) the actual time zones are often not optimal:
The state borders extend for more than 15 degrees of longitude, so that the deviation is greater than the solar time is ± ½ hour. This is applicable in larger countries that want to get by with only one or a few time zones (for example, only one time zone in China).
The reference longitude is not an integral multiple of 15 °, whereby the shift is the time of the adjacent time zones are not ± 1 hour. This has often historical reasons, by no adjustments were made, as the world order was the time zones as a result of the agreement on the prime meridian (examples: Iran, Afghanistan, India, Nepal, Central Australia, Newfoundland).
The reference longitude is outside of the affected (relatively large) area, so that there is a significant departure from the solar time (Examples: France, Spain, Argentina).
World map with the same standard time zones (where there is also a summer time is the winter time), as of: February 2012
Creation of time zones
Originally, each its own place called time clock, which had depended on the sun: when the sun reached its highest point above the horizon, it was 12 noon clock. Passengers were directed to the local time of each reached the place. With the advent of the railroad was a time normally required, which was considered in the broader area of the railway line, to write, for example, general schedules. Thus, the time of a major city, often one of the termini of the railway line to the nationally accepted standard time. This was partly the time of the capital. Examples: Berlin, Hamburg, Munich, Prague, Berne and Geneva time. Was not satisfactory, the situation in cities, where several rail lines ended. Geneva was the terminus for one from Paris and for a Coming from Bern railway line and had the time in Paris and the Berne apart from one’s own time in Geneva.
An improvement was due in the first half of the 19th Century introduced telegraphy. In the 1840-1860s, was established in almost all European countries, a uniform standard time, which could make the country known by telegraphic time signals emitted. They usually chose the time of the respective capital.
The subsequent systematic time zones were first imported from states but from the North American railroad companies 1883rd The run across the continent railroads made more necessary than a standard time. The areas were divided into four (later five) time zones. U.S. and Canada could take over this area with small corrections in later times their state regulations, because they differed from the Greenwich Mean Time (UTC later) for all hours.
The systematic global time zone system was a result of the international agreement of the Greenwich meridian as the prime meridian at the Washington International Meridian Conference 1884th The key for the mapping prime meridian now served as a reference meridian for the subdivision of the earth into time zones.
Unlike in most other countries, in Austria in the mid-19th Century is not the time of the capital, Vienna (16 degrees east longitude), but the Prague time (14.5 degrees east longitude) are used. In the railway sector, however, used depending on the route, the Lindau, Munich, Prague, Budapest or Lemberger time.
Since 1 August 1872 formed the basis for the Vienna meridian determination of time of the train service.  The Vienna lunch time was of the University Observatory at the Vienna train stations signaled by telegraph, of which the noon mark was passed by telegraph to the rear channels.
Due to the experience of Germany was the first October 1891 by the Austrian State Railways, the so-called hour time zone introduced, like in Germany at the time of the 15th eastern longitude referred (CET). For the former Austria with an area of about 9 to 23 Longitude was a good way. A legal regulation in Germany was performed. Since the difference was the Prague time less than two minutes, was the change, at least for the capital city, not very large.
In Switzerland, the foundation of the state in 1848, the Bernese time as the single time. From 1859, the investigation was carried out in the new observatory in Neuchatel, but was still widely translated into Berner time. At least in some places, while simultaneously managing their own time continue to be used, so did the Geneva island tower, for example, in 1880 three watches: The right hand showed the Bernese period, the medium was the time (Berner time -5 minutes) and the left showed the time from Paris or to the railway line to Paris (Berner time -20 minutes).
Due to the introduction of the CET in Germany and Austria adopted the (cantonal) Bernese Government on 18 May 1894 an instruction, after “to avoid confusing Zweispaltigkeit the timing [...] this Central European time even for civil and official life is introduced, and it should all the public clocks (clocks and other church) on the 1st June, next thin advanced by 30 minutes. ” The round number of 30 arose because of Bern has 7.5 ° east longitude. The change has taken part in the Bern canton of the other on the same date.
Zone times map today
Today, the different time zones map to the Coordinated Universal Time (UTC) are (formerly Greenwich Mean Time (GMT)) coupled. The difference from the UTC time zone or adjacent to a constant, usually hours integer value. Countries with very large east-west extension zone usually several times. Besides the U.S., Canada and Russia are Brazil, Mexico and Australia. The People’s Republic of China on the other hand, despite their large east-west extension only, the right to Shanghai and Beijing time zone.
On the continents it is up to each State to regulate its era law. The international harmonization is based on scientific cooperation between the international and national institutions and intergovernmental agreements time.
On the high seas and airspace, as well as in space travel are the practices and standards of the international marine, aviation, and space, beyond the most coming from the military sector national or supranational debt, such as the Nautical time (NATO) are regulated.
Be country-specific time zones, their deviations from UTC time zone or to the neighboring countries are not full hour, for example, are Iran (UTC +3:30 h), Afghanistan (UTC +4:30 h), India (UTC +5:30 h), Nepal (UTC +5:45 h) and the Australian states of Northern Territory and South Australia (UTC +9 30h). 9th December 2007, the world clock back in Venezuela (previously UTC-4h) for half an hour (VST Venezuelan Standard Time, UTC now-4: 30h). The reasons for these special cases are usually the geographic location between two time zones, as well as historical or political.
Politically motivated choice of time zones map
Most countries in the European Union, the CET. In some European countries without a CET, there are always attempts to implement the MDGs and to emphasize the European community. See also state that large communities in the use of multiple time zones is no disadvantage, show the United States. For the territory of the EU, the usual three time zones are relative to the solar time appropriately. France and Spain had begun the process of European integration efforts, instead of the proper UTC ± 0h the MDGs, there in the winter (standard time) deviates significantly from the solar time (in the west of Spain is true noon until about 13:40).
In the People’s Republic of China – whose territory about five time zones (UTC +5 hours to UTC +9 h) would overlap – the political central government decided to use only one time (UTC +8 h). This fits well with the capital Beijing, in the western corner of China is true, but only by 15 noon clock (the clock at 11 eastern).
For commercial reasons, is in the same time as Singapore, Hong Kong, to open the markets of both cities at the same time and close. It is thus the sun by about an hour ahead.
In Nepal, UTC +5:45 hours to get from the big neighbor, India (UTC +5:30 h) delineate.
In Cuba in 2004, decided on the basis of a massive energy crisis, to remain in the summer time. Thus, Cuba had all year until the fall of 2006 UTC 4 hours instead of the geographically “correct” UTC-5h.
Venezuela joined in 1964 from UTC-4: 30h-4h to UTC. On 9 December 2007, under Hugo Chavez, the geographically favorable UTC-4: 30h introduced again. It was also politically motivated: the distinction between practices in the great American neighbors.
In the past, often been imposed on an occupied country, the time zone of occupation. Thus France was changed in 1940 under the German occupation during the Second World War ± 0h UTC to CET. The Netherlands were granted in 1940 by the German occupiers, the CET. This was since 1909 the Amsterdam time (also Dutch time) originally UTC +0:19 h, since 17 March 1937 to UTC +0:20 h rounded. . Even Malaysia was under Japanese occupation in 1942 changed from UTC +7:30 to UTC +9 h h.
Daylight saving time
→ Main article: Daylight saving time
Many countries are changing in the middle of spring in a different time zone, back in the autumn. Shall apply in most EU countries in the winter CET (UTC +1 h), during the summer months, but the Central European Summer Time (BST, UTC +2 h).
One particular change was made in 2011 in Russia. There, it was decided not to give up the summer but the winter time. This meant that all Russian time zones-parts were moved to the easterly each time zone.
In the southern hemisphere (eg in parts of Australia) is set to change about six months in the summer time, so the time difference of these States to Europe during the year, not just one but by two hours vary.
Handling in shipping
→ Main article: Scout (ship)
In east-west or west-east travel on board a ship will be handled the time change quite arbitrarily, and the days when a change occurs, set the operating requirements on board accordingly. In general, in one day moved a maximum of one hour. The day on which the collapse occurs, not necessarily by crossing the geographical border between two time zones. The hour is usually placed in three 20-minute intervals during the night: The first 20 minutes during the 20-24-Clock-guard, the second 20 minutes during the 0-4-Clock-and watch the last 20 minutes during the 4-8-Clock Guard. This ensures that the transition caused by the more-or less work is distributed evenly across all three guards. In two-guard vessels will proceed similarly adjusted and twice in 30 minutes.