词条 世界时（UT）
描述: 世界时，缩写为 UT，是定义时间测量的几种方式的总称。UT1是零经度（格林威治皇家天文台的历史所在地）的平太阳时。平太阳时将一天的长度定义为从一个正午（太阳在天空中的最高位置）到下一个正午之间的平均时间。实际上，必要的测量不是通过太阳，而是通过遥远的天体（如夜间的类星体）进行的。UTC，协调世界时，是一种基于一组特定的大型原子钟（“国际原子时”或 TAI）计时的时间标准，但偶尔会在某些日子添加额外的秒数（“闰秒”），以确保 UTC 和 UT1 的偏差不会超过 0.9 秒。
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The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".
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其他语言版本
- 阿拉伯语: التوقيت العالمي
- 德语: Universalzeit (UT)
- 英语: Universal Time (UT)
- 法语: Temps Universel (UT)
- 意大利语: Tempo Universale (UT)
- 日语: 世界時 (外部链接)
- 巴西葡萄牙语: Horário Universal (UT)
- 繁体中文: 世界時（UT）
相关媒体
Map of de-facto time zones on Earth
图注： Due to the Earth's spherical shape and its rotation around its own axis, local noon – the moment in time when, for an observer at a specific geographic location, the Sun reaches its highest position in the sky varies with longitude. That is why a time coordinate, such as Universal Time (UT or UTC), might be of advantage for specifying moments in time in a unified way. But a global time coordinate will be out of synch with the local day-night rhythm in most locations on Earth. A compromise is to divide Earth into zones each comprising 15 degrees of longitude, and in each zone define time as UTC plus or minus an integer number of hours, with the offset chosen so as to make time match as closely with local time at the middle longitude of the time zone. In practice, political considerations have altered the time zone boundaries somewhat. When a country straddles several time zones, it is not uncommon for the country's government to choose one of those time zones to define the country's official time.
This map, originally created by the CIA and updated by several Wikimedia Commons users, shows the current definitions of the world's time zones. The IAU OAE is not the original author of this map. The designations employed and the presentation of the material on this maps do not imply the expression of any opinion whatsoever on the part of the IAU or the IAU OAE concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.
来源： Wikimedia Users UnaitxuGV, Heitordp and others based on a map created by the U.S. Central Intelligence Agency (CIA)
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License: PD 公共领域 图标
相关图表
International Date Line
图注： The International Date Line (shown here as a solid line) is a specific meridian which roughly follows the meridian of longitude 180°. The International Date Line passes north–south between Russia and Alaska, through the Pacific Ocean including parts of Micronesia and Polynesia, and to the east of Australia/New Zealand before reaching the South Pole on Antarctica. The International Date Line marks the boundary where calendar dates change by one. Therefore, regions to the west of the International Date line are one calendar day ahead of regions to the east.
The International Date Line does not always exactly follow the meridian of longitude 180°. This is partly to stop some territory of a country falling on the other side of the International Date Line than the rest of that country (the Aleutian Islands in the United States being a good example). Some countries also choose which side of the International Date Line they lie on. Samoa changed which side of the date line it lay on in 2011. At this point the International Date Line was moved to lie to the east of Samoa having previously passed to the west of Samoa.
On the opposite side of the world the dashed line marks the prime meridian (the meridian of longitude 0°). This is a line that passes through the Royal Greenwich Observatory in the UK. All time zones are measure relative to Universal Time which is the zero point for all timezones. The time zones marked at the top of the diagram are the timezones in the shaded regions excluding the effects of daylight savings time.
来源： Maria Cristina Fortuna/IAU OAE
