将时区感知日期时间转换为Python中的本地时间 [英] Converting timezone-aware datetime to local time in Python

问题描述

如何将时区感知的datetime对象转换为本地时区的等效非时区感知日期时间？

How do you convert a timezone-aware datetime object to the equivalent non-timezone-aware datetime for the local timezone?

我的特定应用程序使用Django（尽管如此，这实际上是一个通用的Python问题）：

My particular application uses Django (although, this is in reality a generic Python question):

import iso8601

....

date_str="2010-10-30T17:21:12Z"

....

d = iso8601.parse_date(date_str)

foo = app.models.FooModel(the_date=d)
foo.save()

这将导致Django发生错误：

This causes Django to throw an error:

raise ValueError("MySQL backend does not support timezone-aware datetimes.")

我需要的是：

d = iso8601.parse_date(date_str)
local_d = SOME_FUNCTION(d)
foo = app.models.FooModel(the_date=local_d)

SOME_FUNCTION 是

推荐答案

一般来说，要将任意的时区感知日期时间转换为天真（本地）datetime，我会使用 pytz 模块和 astimezone 转换为本地时间，而替换使datetime天真：

In general, to convert an arbitrary timezone-aware datetime to a naive (local) datetime, I'd use the pytz module and astimezone to convert to local time, and replace to make the datetime naive:

In [76]: import pytz

In [77]: est=pytz.timezone('US/Eastern')

In [78]: d.astimezone(est)
Out[78]: datetime.datetime(2010, 10, 30, 13, 21, 12, tzinfo=<DstTzInfo 'US/Eastern' EDT-1 day, 20:00:00 DST>)

In [79]: d.astimezone(est).replace(tzinfo=None)
Out[79]: datetime.datetime(2010, 10, 30, 13, 21, 12)

但是由于您的特定日期时间似乎在UTC时区，您可以这样做：

But since your particular datetime seems to be in the UTC timezone, you could do this instead:

In [65]: d
Out[65]: datetime.datetime(2010, 10, 30, 17, 21, 12, tzinfo=tzutc())

In [66]: import datetime

In [67]: import calendar

In [68]: datetime.datetime.fromtimestamp(calendar.timegm(d.timetuple()))
Out[68]: datetime.datetime(2010, 10, 30, 13, 21, 12)

---

顺便说一下，您可能会将数据时间保存为天真的UTC数据时间而不是天真的本地数据时间这样，您的数据与本地时间无关，您只能在必要时转换为本地时间或任何其他时区。类似于在unicode中工作的类型尽可能多，仅在需要时进行编码。

---

By the way, you might be better off storing the datetimes as naive UTC datetimes instead of naive local datetimes. That way, your data is local-time agnostic, and you only convert to local-time or any other timezone when necessary. Sort of analogous to working in unicode as much as possible, and encoding only when necessary.

所以如果你同意将数据时间存储在天真的UTC中是最好的方法，那么所有你需要做的是定义：

So if you agree that storing the datetimes in naive UTC is the best way, then all you'd need to do is define:

local_d = d.replace(tzinfo=None)

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