Python：如何将日期时间/时间戳从一个时区转换为另一个时区？ [英] Python: How do you convert a datetime/timestamp from one timezone to another timezone?

问题描述

具体来说，给定服务器的时区（系统时间角度）和时区输入，我如何计算系统时间，就像它在那个新时区中一样（不管夏令时如何）？

 导入日期时间
 current_time = datetime.datetime.now（）＃系统时间
 
 server_timezone =美国/东部 
 new_timezone =美国/太平洋地区 
 
 current_time_in_new_timezone = ??? 
  

解决方案

如果您知道原始时区和您想将其转换为它，结果非常简单：

1. 制作一个 pytz.timezone 当前时区和新时区的对象，例如 pytz.timezone（美国/太平洋）。如果您不知道时区的正式名称，只需调用 pytz.all_timezones

   
   
   

2. 使用当前时区的pytz对象以及您的datetime / timestamp作为输入，调用 .localize（）以将其本地化为当前时区。例如 current_timezone.localize（timestamp）

   
   



3. 最后，致电 .astimezone（）在步骤2中新定位的日期时间/时间戳上，并以所需的新时区的pytz对象作为输入，例如 localized_timestamp.astimezone（new_timezone）。

   
   

完成！ / p>

完整示例：

 导入日期时间
导入pytz 
 
＃一个时间戳，我想转换
 my_timestamp = datetime.datetime.now（）
 
＃创建两个时区对象
 old_timezone = pytz.timezone（ US /东部）
 new_timezone = pytz.timezone（美国/太平洋）
 
＃两步处理
 localized_timestamp = old_timezone.localize（my_timestamp）
 new_timezone_timestamp = localized_timestamp.astimezone（new_timezone）
 
＃或作为单线
 new_timezone_timestamp = old_timezone.localize（my_timestamp）.astimezone（new_timezone）
  

奖金：但是，如果您需要的只是特定时区的当前时间，则可以方便地将该时区直接传递到datetime.now（）以获取当前时间直接：

  datetime.datetime.now（new_timezone）
  

一般而言，在需要进行时区转换时，我强烈建议您应将所有时间戳存储在UTC的数据库中。没有夏令时（DST）过渡。作为一种好习惯，应该始终选择启用时区支持（即使您的用户都在一个时区中！）。这将帮助您避免困扰着当今众多软件的DST过渡问题。

除了DST之外，软件时间通常还很棘手。为了大致了解在软件中处理时间有多困难，这里提供了一个潜在的启发性资源： http：// yourcalendricalfallacyis.com

即使将日期时间/时间戳转换为日期也看似简单，但操作似乎并不明显。正如此有用的文档指出的那样：

日期时间表示时间点。绝对是绝对的：它不依赖任何内容。相反，日期是一个日历概念。这是一个时间段，其范围取决于考虑日期的时区。如您所见，这两个概念在根本上是不同的。

了解这一区别是避免基于时间的错误的关键一步。祝你好运。

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)?

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

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

current_time_in_new_timezone = ???

解决方案

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

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

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)

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).

Done!

As a full example:

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 = 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:

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.

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

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

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.

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

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