blocks|key|252574|text|Epoch+time+(unix时间)是一个标准术语：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|252575|http://en.wikipedia.org/wiki/Unix_time|offset|length|252576|252577|+Unix时间，或POSIX时间，是一种用于描述时间实例的系统，定义为自协调世界时(UTC)于1970年1月1日午夜以来所经过的秒数，注释1不包括leap+seconds.note+2。它在类Unix和许多其他操作系统和文件格式中被广泛使用。它既不是时间的线性表示，也不是UTC.note+3+Unix时间的真实表示。在某些Unix系统上，可以通过在命令行中键入date+%2B%25s来检查|blockquote|252578|252579|252580|这意味着如果你通过Python使用纪元时间，它将在不同的平台上保持一致。保持一致性的最好办法是在所有情况下都使用UTC。|252581|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|12|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@$D|W|E|X|1|Y]]|A|$]]|$1|F|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|G|3|H|5|I|7|10|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|12|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|13|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|O|$P|$5|Q|R|S|A|$T|C]]]]

Epoch time (unix time) is a standard term:

<a href="http://en.wikipedia.org/wiki/Unix_time" rel="nofollow">http://en.wikipedia.org/wiki/Unix_time</a>

<blockquote>
 Unix time, or POSIX time, is a system for describing instances in
 time, defined as the number of seconds that have elapsed since
 midnight Coordinated Universal Time (UTC), 1 January 1970,[note 1] not
 counting leap seconds.[note 2] It is used widely in Unix-like and many
 other operating systems and file formats. It is neither a linear
 representation of time nor a true representation of UTC.[note 3] Unix
 time may be checked on some Unix systems by typing date +%s on the
 command line
</blockquote>

That means if you use the epoch times through Python, it will be consistent across platforms. Your best bet for consistency is to use UTC in all cases.

blocks|key|975969|text|time()总是返回来自纪元的时间，看看documentation。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|975970|请注意，Epoch始终是1970年以来的秒数，但由于不同机器上的时钟不同-您可能会遇到一些问题。|975971|引文：|975972|975973|纪元是时间开始的点。在那一年的1月1日，在零点，“自纪元以来的时间”是零。对于Unix，纪元是1970年。要找出纪元是什么，请查看gmtime(0)。|blockquote|975974|975975|975976|和：|975977|975978|+time.time()？|975979|975980|以浮点数的形式返回自纪元以来的时间(秒)。请注意，尽管时间总是以浮点数的形式返回，但并非所有系统都提供比1秒更高的时间精度。虽然此函数通常返回非递减的值，但如果系统时钟在两次调用之间被调回，则它可以返回比前一次调用更低的值。|975981|975982|(都来自Python文档)。|975983|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/2/library/time.html#time.time^0|0|6|K|D|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|18|8|@$9|19|A|1A|B|C]]|D|@$9|1B|A|1C|1|1D]]|E|$]]|$1|F|3|G|5|6|7|1E|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|1F|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|1G|8|@]|D|@]|E|$]]|$1|K|3|L|5|M|7|1H|8|@]|D|@]|E|$]]|$1|N|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]|$1|P|3|Q|5|6|7|1K|8|@]|D|@]|E|$]]|$1|R|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]|$1|S|3|T|5|M|7|1M|8|@]|D|@]|E|$]]|$1|U|3|-4|5|6|7|1N|8|@]|D|@]|E|$]]|$1|V|3|W|5|6|7|1O|8|@]|D|@]|E|$]]|$1|X|3|-4|5|6|7|1P|8|@]|D|@]|E|$]]|$1|Y|3|Z|5|6|7|1Q|8|@]|D|@]|E|$]]|$1|10|3|-4|5|6|7|1R|8|@]|D|@]|E|$]]]|11|$12|$5|13|14|15|E|$16|17]]]]

<code>time()</code> would always return the time from epoch, look at the <a href="http://docs.python.org/2/library/time.html#time.time" rel="nofollow">documentation</a>.

Please note that Epoch is always the number of seconds since 1970, but since the clock on different machines are not the same - you'll might experience some problems.

Citation:

<blockquote>
 The epoch is the point where the time starts. On January 1st of that
 year, at 0 hours, the “time since the epoch” is zero. For Unix, the
 epoch is 1970. To find out what the epoch is, look at gmtime(0).
</blockquote>

And:

<blockquote>
 time.time()¶
 
 Return the time in seconds since the epoch as a floating
 point number. Note that even though the time is always returned as a
 floating point number, not all systems provide time with a better
 precision than 1 second. While this function normally returns
 non-decreasing values, it can return a lower value than a previous
 call if the system clock has been set back between the two calls.
</blockquote>

(Both from Python documentation).

blocks|key|976027|text|The+documentation说：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|976028|976029|要找出纪元是什么，请查看gmtime(0)。|blockquote|style|CODE|976030|976031|976032|我会将此解释为没有特定的时代是有保证的。|976033|另请参见this+Python-Dev+thread。这似乎证实了这样的观点，即在实践中，纪元总是被假定为1970/01/01，但语言并没有明确保证这一点。|976034|这样做的结果是，至少对于Python，您可能可以使用纪元时间，除非您正在处理陌生和晦涩的平台。对于使用非Python工具进行阅读，您可能也没问题，但要特别确保您需要阅读这些工具提供的文档。|976035|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/2/library/time.html|1|http://grokbase.com/t/python/python-dev/086gxjdb5a/epoch-and-platform^0|0|H|0|0|0|C|9|0|0|0|0|4|M|1|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@$A|12|B|13|1|14]]|C|$]]|$1|D|3|-4|5|6|7|15|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|16|8|@$A|17|B|18|H|I]]|9|@]|C|$]]|$1|J|3|-4|5|6|7|19|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]|$1|L|3|M|5|6|7|1B|8|@]|9|@]|C|$]]|$1|N|3|O|5|6|7|1C|8|@]|9|@$A|1D|B|1E|1|1F]]|C|$]]|$1|P|3|Q|5|6|7|1G|8|@]|9|@]|C|$]]|$1|R|3|-4|5|6|7|1H|8|@]|9|@]|C|$]]]|S|$T|$5|U|V|W|C|$X|Y]]|Z|$5|U|V|W|C|$X|10]]]]

<a href="http://docs.python.org/2/library/time.html" rel="noreferrer">The documentation</a> says:

<blockquote>
 To find out what the epoch is, look at <code>gmtime(0)</code>.
</blockquote>

I would interpret this to mean that no particular epoch is guaranteed.

See also <a href="http://grokbase.com/t/python/python-dev/086gxjdb5a/epoch-and-platform" rel="noreferrer">this Python-Dev thread</a>. That seems to confirm the notion that, in practice, the epoch is always assumed to be 1970/01/01, but that this is not explicitly guaranteed by the language.

The upshot of this is that, at least for Python, you're probably okay using epoch time unless you're dealing with strange and obscure platforms. For reading with non-Python tools, you're probably also okay, but to be extra sure you'd need to read the documentation those tools provide.

blocks|key|4808063|text|Micropython's纪元为1/1/2000，请参阅time()+Micropython's+utime。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4808064|entityMap|0|LINK|mutability|MUTABLE|url|http://www.micropython.org/|1|http://docs.micropython.org/en/latest/wipy/library/time.html#time.time|2|3|https://docs.micropython.org/en/latest/pyboard/library/utime.html^0|0|D|0|S|6|1|Z|D|2|1D|5|3|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]|$A|U|B|V|1|W]|$A|X|B|Y|1|Z]|$A|10|B|11|1|12]]|C|$]]|$1|D|3|-4|5|6|7|13|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]|N|$5|G|H|I|C|$J|K]]|O|$5|G|H|I|C|$J|P]]]]

<a href="http://www.micropython.org/" rel="nofollow noreferrer">Micropython's</a> epoch is 1/1/2000, see <a href="http://docs.micropython.org/en/latest/wipy/library/time.html#time.time" rel="nofollow noreferrer">time()</a> and <a href="https://docs.micropython.org/en/latest/pyboard/library/utime.html" rel="nofollow noreferrer">utime</a>.

blocks|key|4325742|text|在Python+pandas.to_datetime()中，虽然缺省值是unix纪元起源，但您可以通过提供自定义引用时间戳来更改它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4325743|例如,|4325744|pd.to_datetime(18081)+#default+unix+epoch
Out:+Timestamp('1970-01-01+00:00:00.000018081')+#default+is+in+nanosecond

pd.to_datetime(18081,+unit='D')
Out:+Timestamp('2019-07-04+00:00:00')+#change+unit+of+measure|code-block|syntax|javascript|4325745|您可以将其更改为任何参考日期。确保单元是合理的。在下面的示例中，我们将原点设置为1960年1月1日。请注意，这是默认的SAS日期开始日期。|4325746|pd.to_datetime(18081,+unit='D',++origin='1960-1-1')+#change+to+your+reference+start+date
Out:+Timestamp('2009-07-03+00:00:00')|4325747|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

In Python pandas.to_datetime(), while the default is unix epoch origin, you can change it by providing your custom reference timestamp. 

For example, 

<pre><code>pd.to_datetime(18081) #default unix epoch
Out: Timestamp('1970-01-01 00:00:00.000018081') #default is in nanosecond

pd.to_datetime(18081, unit='D')
Out: Timestamp('2019-07-04 00:00:00') #change unit of measure
</code></pre>

You can change it to any reference date. Make sure the unit is reasonable. In example below, we set the origin to January 1, 1960. Note that this is default SAS date start date. 

<pre><code>pd.to_datetime(18081, unit='D', origin='1960-1-1') #change to your reference start date
Out: Timestamp('2009-07-03 00:00:00')
</code></pre>

Is the epoch start time in Python independent of the platform (i.e. always 1/1/1970)?

Or is it platform dependent?

I want to serialize datetimes (with second accuracy) on various machines running Python, and be able to read them back on different platforms, possibly also using different programming languages (than Python). Is serializing epoch time a good idea?

In Python, is epoch time returned by time() always measured from Jan 1, 1970?

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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Python中的纪元开始时间是否独立于平台(例如，总是1/1/1970)？或者它依赖于平台？我想在运行Python的各种机器上序列化datetimes (以第二精度)，并且能够在不同的平台上读回它们，可能也使用不同的编程语言(而不是Python)。序列化纪元时间是个好主意吗？

问在Python中，time()返回的纪元时间总是从1970年1月1日开始测量的吗？
EN

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问在Python中，time()返回的纪元时间总是从1970年1月1日开始测量的吗？EN