A time zone is a geographic region of the globe that observes a uniform standard civil time for legal, commercial, and social purposes.

How do time zones work?

Because Earth rotates 360 degrees in 24 hours, the planet is divided into 24 theoretical longitudinal sections of roughly 15 degrees each. Civil boundaries are adjusted along national and administrative borders, with each zone defining its standard time as an offset from the Prime Meridian.

What is a UTC offset?

A UTC offset is the difference in hours and minutes between a region standard civil time and Coordinated Universal Time (UTC). Offsets range from UTC-12:00 in the western Pacific to UTC+14:00 in the Line Islands.

Why do some time zones have 30-minute or 45-minute offsets?

Several jurisdictions—such as India (UTC+5:30), Iran (UTC+3:30), and Nepal (UTC+5:45)—chose half-hour or 45-minute fractional offsets so that civil time corresponds more naturally with the midpoint of solar noon across their national landmass.

Why do some countries have multiple time zones?

Large countries spanning broad east-to-west geographic distances (such as the United States, Canada, Russia, and Australia) observe multiple time zones so that daylight hours stay roughly aligned with morning and evening civil routines across the nation.

How is local time calculated from UTC?

Local time is calculated by taking the current UTC time and adding the region positive offset (if located east of the Prime Meridian) or subtracting its negative offset (if located west of the Prime Meridian), including any active daylight saving adjustment.

What is daylight saving time?

Daylight Saving Time (DST) is the seasonal practice of advancing clocks by one hour during spring and summer months to extend daylight into civil evening hours, before resetting back to standard time in autumn.

Why do time-zone differences change during the year?

The time difference between two locations changes when one location observes seasonal daylight saving adjustments while the other maintains standard time, or when both observe daylight saving on different transition schedules.

World Time Zones Directory & World Time Zone List

全球时区原理：经度、太阳正午与 24 小时制

地球每 24 小时自转 360 度，太阳正午在各地依次发生。19 世纪末，桑福德·弗莱明爵士提议将全球划分为 24 个标准时区，每区横跨约 15 个经度（360° / 24 = 15°/小时）。

全球时区以经过英国格林尼治的本初子午线（0°经线）为基准确立协调世界时 (UTC)。其正对面的太平洋中央则是国际日界线。

尽管理论时区宽度为 15 度，实际行政时区则依国界而定。部分国家还采用半小时或 45 分钟的特殊偏差（如印度 UTC+5:30、尼泊尔 UTC+5:45）。

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🌍 全球主要城市与国际时区目录

🌍 Time Zones Guide

常见问题解答 (FAQ)

Common questions about how world time zones, UTC offsets, and civil boundaries function.

什么是时区？

时区是指为了法律、商业和社会交流的便利，而在全球范围内划分的统一遵守相同标准时间的地理区域。

时区是如何运作和划分的？

由于地球在24小时内自转360度，全球理论上被划分为24个各约15个经度的时区。实际行政边界则根据国家和区域界线调整，并以本初子午线（UTC）的偏移量来统一定义。

什么是 UTC 偏移量？

UTC偏移量是指某一地区的本地法定标准时间与协调世界时（UTC）之间的小时和分钟差额。全球偏移量范围从西太平洋的 UTC-12:00 一直延伸到莱恩群岛的 UTC+14:00。

为什么有些时区会有30分钟或45分钟的奇数偏移量？

印度（UTC+5:30）、伊朗（UTC+3:30）和尼泊尔（UTC+5:45）等国家采用半小时或45分钟的非常规偏移，是为了让本国领土的太阳正午与日常作息正午更加吻合。

为什么有些国家拥有多个时区？

东西跨度辽阔的大国（如美国、加拿大、俄罗斯和澳大利亚）设有多个时区，以确保全国各地的日出日落与当地居民的早晚工作作息大致保持同步。

如何通过 UTC 计算当地时间？

计算方式为：以当前的UTC时间为基准，位于格林尼治子午线以东的地区加上正偏移量，以西的地区减去负偏移量，并在适用时计入夏令时的1小时调整。

什么是夏令时（DST）？

夏令时（DST）是在春夏季节将时钟调快一小时以充分利用傍晚自然光照，并在秋冬季节恢复为标准时间的季节性制度。

为什么一年中国际时差会发生变化？

当一地实行夏令时而另一地全年保持标准时间，或者两地采用不同的夏令时切换日期时，两座城市之间的实际时差就会发生增减变动。

世界时区大全目录与全球城市实时时间

全球时区原理：经度、太阳正午与 24 小时制

什么是 UTC？（协调世界时）

夏令时 (DST) 深度解析

世界时区缩写词典

🌍 全球主要城市与国际时区目录

North America (36 cities)

Europe (73 cities)

Europe / Asia (7 cities)

Asia (59 cities)

Oceania (14 cities)

South America (17 cities)

Africa (12 cities)

常见问题解答 (FAQ)

世界时区大全目录与全球城市实时时间

全球时区原理：经度、太阳正午与 24 小时制

什么是 UTC？（协调世界时）

夏令时 (DST) 深度解析

世界时区缩写词典

🌍 全球主要城市与国际时区目录

North America (36 cities)

Europe (73 cities)

Europe / Asia (7 cities)

Asia (59 cities)

Oceania (14 cities)

South America (17 cities)

Africa (12 cities)

常见问题解答 (FAQ)

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