blocks|key|1286081|text|Etc/UTC是显示名称为UTC的时区。也就是说，根据IANA时区数据库，它们是同一个时区的长名称和短名称。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1286082|entityMap|0|LINK|mutability|MUTABLE|url|ftp://ftp.iana.org/tz/data/etcetera^0|0|7|D|3|R|9|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@$9|S|A|T|1|U]]|E|$]]|$1|F|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

<code>Etc/UTC</code> is the time zone whose display name is <code>UTC</code>. That is, they're long and short names for the same timezone, per <a href="ftp://ftp.iana.org/tz/data/etcetera" rel="nofollow noreferrer">IANA's time zone database</a>.

blocks|key|2555111|text|ETC/GMT%2B4与GMT-4相同。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2555112|public+static+void+main(String[]+args)+{
++++TimeZone+tz+=+TimeZone.getTimeZone("Etc/GMT-7");
++++System.out.println(tz);

++++tz+=+TimeZone.getTimeZone("GMT%2B7");
++++System.out.println(tz);

}|code-block|syntax|javascript|2555113|你可以自己测试。|2555114|但我不知道这是什么意思。|2555115|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

ETC/GMT+4 is the same as GMT-4.

<pre><code>public static void main(String[] args) {
 TimeZone tz = TimeZone.getTimeZone("Etc/GMT-7");
 System.out.println(tz);

 tz = TimeZone.getTimeZone("GMT+7");
 System.out.println(tz);

}
</code></pre>

You can test it by yourself.

But I don't know what ETC mean..

blocks|key|1286167|text|第一，回答问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1286168|UTC和Etc/UTC时区之间没有差异。|offset|length|style|CODE|1286169|Etc/UTC是Olson数据库(tz数据库)中的一个时区，也称为IANA-时区-数据库，其中所有时区都符合统一的命名约定：Area/Location。|1286170|由于某些时区不能归属于世界上任何地区(即大陆或海洋)，因此引入了特殊区域Etc+(以此类推)。这主要适用于管理时区(如UTC+)。|1286171|因此，为了符合命名约定，在tz数据库中将通用协调时间(Zone)命名为Etc/UTC。|1286172|对于UTC以外的管理时区(例如GMT%2B4、GMT-8)，tz数据库在区域名称中使用POSIX-风格标志。对于位于格林威治之后(格林威治以西)的地区，POSIX有积极的迹象，而在格林威治以东的地区，则有负面的迹象。|1286173|时区内的POSIX样式标志与时区的定义是截然相反的，在当今广泛使用的ISO+8601中。在ISO+8601时区格式中，负号表示一个区域落后于UTC+(格林威治以西)，正标志表示一个区域在UTC+(格林威治以东)之前。这就是现在的标准用法。|1286174|POSIX中可能出现相反定义的原因是：|1286175|POSIX是UNIX的一部分，UNIX是在美国开发的，它落后于UTC+(格林威治以西)。POSIX格式允许将美国时区表示为EST5，PST8，即省略(%2B)符号。|unordered-list-item|1286176|通常，计算机程序和操作系统在UTC时间内做任何事情。使用POSIX风格的标志，您可以添加时间和时区，以获得UTC时间。例如："03:30+PST8“或"03:30+GMT%2B8”指的是“世界协调时11:30”。|1286177|entityMap|0|LINK|mutability|MUTABLE|url|https://en.wikipedia.org/wiki/Tz_database|1|https://www.iana.org/time-zones|2|https://www.ietf.org/timezones/data/etcetera|3|http://www.ibm.com/developerworks/aix/library/au-aix-posix/index.html#10.UnderstandthePOSIXformat%257Coutline|4|https://en.wikipedia.org/wiki/ISO_8601#Time_offsets_from_UTC^0|0|0|3|4|7|0|0|7|1Q|D|H|5|0|X|B|1|0|10|3|1N|3|15|4|2|0|Z|7|0|F|5|L|5|15|A|3|0|Y|8|4|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1E|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1F|8|@$D|1G|E|1H|F|G]|$D|1I|E|1J|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|1K|8|@$D|1L|E|1M|F|G]|$D|1N|E|1O|F|G]]|9|@$D|1P|E|1Q|1|1R]|$D|1S|E|1T|1|1U]]|A|$]]|$1|J|3|K|5|6|7|1V|8|@$D|1W|E|1X|F|G]|$D|1Y|E|1Z|F|G]]|9|@$D|20|E|21|1|22]]|A|$]]|$1|L|3|M|5|6|7|23|8|@$D|24|E|25|F|G]]|9|@]|A|$]]|$1|N|3|O|5|6|7|26|8|@$D|27|E|28|F|G]|$D|29|E|2A|F|G]]|9|@$D|2B|E|2C|1|2D]]|A|$]]|$1|P|3|Q|5|6|7|2E|8|@]|9|@$D|2F|E|2G|1|2H]]|A|$]]|$1|R|3|S|5|6|7|2I|8|@]|9|@]|A|$]]|$1|T|3|U|5|V|7|2J|8|@]|9|@]|A|$]]|$1|W|3|X|5|V|7|2K|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|2L|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]|16|$5|11|12|13|A|$14|17]]|18|$5|11|12|13|A|$14|19]]|1A|$5|11|12|13|A|$14|1B]]|1C|$5|11|12|13|A|$14|1D]]]]

Firstly, to answer the question: 
There is NO difference between <code>UTC</code> and <code>Etc/UTC</code> time zones.

<code>Etc/UTC</code> is a timezone in the Olson-timezone-database (<a href="https://en.wikipedia.org/wiki/Tz_database">tz database</a>), also known as <a href="https://www.iana.org/time-zones">IANA-timezones-database</a>, in which all timezones conform to a uniform naming convention: <code>Area/Location</code>.

Since, some timezones cannot be attributed to any Area of the world (i.e. continents or oceans), the special Area <code>Etc</code> (<a href="https://www.ietf.org/timezones/data/etcetera">Etcetera</a>) was introduced. This applies mainly to administrative timezones such as <code>UTC</code>. 
Thus, to conform with the naming convention, the universal coordinated time(zone) is named <code>Etc/UTC</code> in the tz database.

For administrative timezones other than UTC (e.g. <code>GMT+4</code>, <code>GMT-8</code>), the tz database uses <a href="http://www.ibm.com/developerworks/aix/library/au-aix-posix/index.html#10.UnderstandthePOSIXformat%7Coutline">POSIX-style signs</a> in the zone-names. POSIX has positive signs for zones that are behind Greenwich (west of Greenwich) and negative signs for zones that are ahead of Greenwich (east of Greenwich).

POSIX-style signs in timezones are the opposite of the definition of timezones in the nowadays widespread and mostly used <a href="https://en.wikipedia.org/wiki/ISO_8601#Time_offsets_from_UTC">ISO 8601</a>. In the ISO 8601 timezone format, negative signs indicate a zone is behind UTC (west of Greenwich) and positive signs indicate a zone is ahead of UTC (east of Greenwich). This is what has become the standard usage nowadays.

Possible reasons for the opposite definition in POSIX are:

<ul>
<li>POSIX is part of UNIX, which was developed in the USA, which is behind UTC (west of Greenwich). The POSIX format allows the US timezones to be represented as EST5, PST8, i.e. omitting the (+) sign.</li>
<li>Usually, computer programs and operating systems internally do everything in UTC time. With POSIX-style signs you can add time and timezone in order to get UTC time. Example: "03:30 PST8" or "03:30 GMT+8" mean it is "11:30 UTC".</li>
</ul>

In the PHP documentation, <a href="http://php.net/manual/en/timezones.others.php">list of supported time zones</a>, <code>UTC</code> is listed twice:

<ul>
<li><code>UTC</code></li>
<li><code>Etc/UTC</code></li>
</ul>

Is there any conceptual difference between those two, or are they just synonyms?

Is there a difference between the UTC and Etc/UTC time zones?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在PHP文档中，、UTC列出了两次：UTCEtc/UTC这两者在概念上有什么区别，还是只是同义词？

问UTC和Etc/UTC时区之间有什么区别吗？
EN

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问UTC和Etc/UTC时区之间有什么区别吗？EN