Python：如何将日期时间/时间戳从一个时区转换为另一个时区？

Python: How do you convert a datetime/timestamp from one timezone to another timezone?

提问by kfan

Specifically, given the timezone of my server (system time perspective) and a timezone input, how do I calculate the system time as if it were in that new timezone (regardless of daylight savings, etc)?

具体来说，鉴于我的服务器的时区（系统时间透视图）和时区输入，我如何计算系统时间，就好像它在新时区中一样（不管夏令时等）？

import datetime
current_time = datetime.datetime.now() #system time

server_timezone = "US/Eastern"
new_timezone = "US/Pacific"

current_time_in_new_timezone = ???

采纳答案by kfan

If you know your origin timezone and the new timezone that you want to convert it to, it turns out to be very straightforward:

如果您知道您的原始时区和要将其转换为的新时区，结果会非常简单：

1) Make a pytz.timezoneobject for both the current timezone and the new timezone e.g. pytz.timezone("US/Pacific"). If you don't know a timezone's official name, you can find a list of all official timezones by simply calling pytz.all_timezones

1）pytz.timezone为当前时区和新时区创建一个对象，例如pytz.timezone("US/Pacific")。如果您不知道时区的官方名称，只需拨打以下电话即可找到所有官方时区的列表pytz.all_timezones

2) Call .localize()using the current timezone's pytz object with your datetime/timestamp as input to localize it to the current timezone. e.g. current_timezone.localize(timestamp)

2).localize()使用当前时区的 pytz 对象和日期时间/时间戳作为输入调用以将其本地化到当前时区。例如current_timezone.localize(timestamp)

3) Finally, call .astimezone()on the newly localized datetime/timestamp from step 2 with the desired new timezone's pytz object as input e.g. localized_timestamp.astimezone(new_timezone).

3) 最后，.astimezone()使用所需的新时区的 pytz 对象作为输入调用步骤 2 中新本地化的日期时间/时间戳，例如localized_timestamp.astimezone(new_timezone).

Done!

完毕！

As a full example:

作为一个完整的例子：

import datetime
import pytz

# a timestamp I'd like to convert
my_timestamp = datetime.datetime.now()

# create both timezone objects
old_timezone = pytz.timezone("US/Eastern")
new_timezone = pytz.timezone("US/Pacific")

# two-step process
localized_timestamp = old_timezone.localize(my_timestamp)
new_timezone_timestamp = timezone_localized_timestamp.astimezone(new_timezone)

# or alternatively, as an one-liner
new_timezone_timestamp = old_timezone.localize(my_timestamp).astimezone(new_timezone) 

Bonus: but if all you need is the current time in a specific timezone, you can conveniently pass that timezone directly into datetime.now() to get the current times directly:

奖励：但如果您只需要特定时区中的当前时间，您可以方便地将该时区直接传递给 datetime.now() 以直接获取当前时间：

datetime.datetime.now(new_timezone)

When it comes to needing timezones conversions generally, I would strongly advise that one should store all timestamps in your database in UTC, which has no daylight savings time (DST) transition. And as a good practice, one should always choose to enable time zone support (even if your users are all in a single time zone!). This will help you avoid the DST transition problem that plagues so much software today.

当谈到通常需要时区转换时，我强烈建议您将所有时间戳以 UTC 格式存储在您的数据库中，它没有夏令时 (DST) 转换。作为一种好的做法，应该始终选择启用时区支持（即使您的用户都在一个时区！）。这将帮助您避免困扰当今众多软件的 DST 转换问题。

Beyond DST, time in software can be generally quite tricky. To get a sense of just how difficult it is to deal with time in software in general, here is a potentially enlightening resource: http://yourcalendricalfallacyis.com

除了夏令时，软件中的时间通常非常棘手。为了大致了解在软件中处理时间是多么困难，这里有一个潜在的启发性资源：http: //yourcalendricalfallacyis.com

Even a seemingly simple operation as converting a datetime/timestamp into a date can become non-obvious. As this helpful documentationpoints out:

即使是将日期时间/时间戳转换为日期的看似简单的操作也可能变得不明显。正如这个有用的文档指出的那样：

A datetime represents a point in time. It's absolute: it doesn't depend on anything. On the contrary, a date is a calendaring concept. It's a period of time whose bounds depend on the time zone in which the date is considered. As you can see, these two concepts are fundamentally different.

日期时间代表一个时间点。这是绝对的：它不依赖于任何东西。相反，日期是一个日历概念。这是一段时间，其界限取决于考虑日期的时区。如您所见，这两个概念有着根本的不同。

Understanding this difference is a key step towards avoiding time-based bugs. Good luck.

了解这种差异是避免基于时间的错误的关键一步。祝你好运。

回答by jfs

How do you convert datetime/timestamp from one timezone to another timezone?

如何将日期时间/时间戳从一个时区转换为另一个时区？

There are two steps:

有两个步骤：

1. Create an aware datetime objects from the system time and timezonee.g., to get the current system time in the given timezone:

   #!/usr/bin/env python
   from datetime import datetime
   import pytz
   
   server_timezone = pytz.timezone("US/Eastern")
   server_time = datetime.now(server_timezone) # you could pass *tz* directly
   

   Note: datetime.now(server_timezone)works even during ambiguous timese.g., during DST transitions while server_timezone.localize(datetime.now())may fail (50% chance).

   If you are sure that your input time exists in the server's timezone and it is unique then you could pass is_dst=Noneto assert that:

   server_time = server_timezone.localize(naive_time, is_dst=None)
   

   It raises an exception for invalid times.
   If it is acceptable to ignore upto a dayerror (though typically an error due to DST is around an hour) then you could drop is_dstparameter:

   server_time = server_timezone.normalize(server_timezone.localize(naive_time))
   

   .normalize()is called to adjust non-existing times (local time in the gap, during "spring forward" transitions). If the time zone rules haven't changed; your server shouldn't generate non-existing times. See "Can I just always set is_dst=True?"

2. Convert an aware datetime object to the target timezone tz:

   tz = pytz.timezone("US/Pacific")
   server_time_in_new_timezone = server_time.astimezone(tz)
   

1. 从系统时间和时区创建一个感知日期时间对象，例如，获取给定时区中的当前系统时间：

   #!/usr/bin/env python
   from datetime import datetime
   import pytz
   
   server_timezone = pytz.timezone("US/Eastern")
   server_time = datetime.now(server_timezone) # you could pass *tz* directly
   

   注意：datetime.now(server_timezone)即使在不明确的时间也能工作，例如在 DST 转换期间，但server_timezone.localize(datetime.now())可能会失败（50% 的几率）。

   如果您确定您的输入时间存在于服务器的时区中并且它是唯一的，那么您可以通过is_dst=None断言：

   server_time = server_timezone.localize(naive_time, is_dst=None)
   

   它引发无效时间的异常。
   如果可以忽略最多一天的错误（尽管通常由于 DST 导致的错误大约是一个小时），那么您可以删除is_dst参数：

   server_time = server_timezone.normalize(server_timezone.localize(naive_time))
   

   .normalize()被调用来调整不存在的时间（间隙中的本地时间，在“spring forward”转换期间）。如果时区规则没有改变；您的服务器不应生成不存在的时间。请参阅“我可以始终设置 is_dst=True 吗？”

2. 将感知日期时间对象转换为目标时区tz：

   tz = pytz.timezone("US/Pacific")
   server_time_in_new_timezone = server_time.astimezone(tz)