将datetime打印为pytz.timezone（“ Etc / GMT-5”）会产生错误的结果 [英] Printing datetime as pytz.timezone("Etc/GMT-5") yields incorrect result

问题描述

请考虑以下示例，在该示例中，我采用了一个简单的日期时间，使其在UTC中变为时区，然后转换为UTC-5：

Consider the following example, where I take a naive datetime, make it timezone aware in UTC, and then convert to UTC-5:

d1 = datetime.datetime(2019,3,7, 7,45)

d2 = pytz.utc.localize(d1)
print(f'UTC  : {d2}')

d3 = d2.astimezone(pytz.timezone('Etc/GMT-5'))
print(f'UTC-5: {d3}')

其输出为：

UTC  : 2019-03-07 07:45:00+00:00
UTC-5: 2019-03-07 12:45:00+05:00

我希望 UTC -5 时间为 02:45 ，但是5小时的偏移量是添加到UTC，而不是减去。

I would have expected the UTC-5 time to be 02:45, but the 5 hour offset is being added to UTC, rather than subtracted.

问题：

• 为什么'Etc / GMT-5'应用于UTC +5小时而不是-5小时的偏移量？


• 如何从 UTC 到 UTC-5 ？

• Why is the 'Etc/GMT-5' offset applied to UTC +5 hours instead of -5 hours?
• How can I convert from UTC to UTC-5?

推荐答案

您正在使用 pytz ，而不仅仅是Python的 datetime 。
像dateutil ，pytz 使用Olson tz数据库。

You are using pytz, not just Python's datetime. Like dateutil, pytz uses the Olson tz database.

Olson tz数据库定义了 Etc / GMT + N 符合POSIX风格的时区：

The Olson tz database defines Etc/GMT+N timezones which conform with the POSIX style:

以
开头的区域名称 Etc / GMT的符号与标准ISO 8601约定相反。在
中的 Etc区域中，GMT以西的区域带有正号，而东部的区域则带有
负号（例如， Etc / GMT-14比GMT早14小时。）

those zone names beginning with "Etc/GMT" have their sign reversed from the standard ISO 8601 convention. In the "Etc" area, zones west of GMT have a positive sign and those east have a negative sign in their name (e.g "Etc/GMT-14" is 14 hours ahead of GMT.)

---

因此，要将UTC转换为偏移量为-5的时区，可以使用 Etc / GMT + 5 ：

import datetime as DT
import pytz

naive = DT.datetime(2019, 3, 7, 7, 45)
utc = pytz.utc
gmt5 = pytz.timezone('Etc/GMT+5')
print(utc.localize(naive).astimezone(gmt5))

# 2019-03-07 02:45:00-05:00

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