Python datetime.utcnow() 返回不正确的日期时间
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Python datetime.utcnow() returning incorrect datetime
提问by Johann Gomes
datetime.utcnow()
This call is returning an incorrect datetime, delayed from UTC/GMT by 1 hour (check in: http://www.worldtimeserver.com/current_time_in_UTC.asp).
此调用返回不正确的日期时间，从 UTC/GMT 延迟 1 小时（请登录：http: //www.worldtimeserver.com/current_time_in_UTC.asp）。
Is it working like it should be?
它是否像应有的那样工作？
For example, it's returning, right now:
例如，它现在正在返回：
2015-02-17 23:58:44.761000.
Current UTC time is: 00:58, not 23:58
当前 UTC 时间是：00:58，而不是 23:58
回答by jfs
datetime.utcnow()uses OS provided values.
datetime.utcnow()使用操作系统提供的值。
datetime.utcnow()uses gettimeofday(2)or time.time()on Python 2 (and gmtime(3)to convert the result into broken-down time).
datetime.utcnow()在 Python 2 上使用gettimeofday(2)或time.time()（gmtime(3)并将结果转换为故障时间）。
time.time()uses gettimeofday(2), ftime(3), time(2). Newer CPython versions may use clock_gettime(2), GetSystemTimeAsFileTime().
time.time()使用gettimeofday(2), ftime(3), time(2). 较新的 CPython 版本可能使用clock_gettime(2),GetSystemTimeAsFileTime().
You could check the self-consistency as follows:
您可以按如下方式检查自洽性：
#!/usr/bin/env python
import time
from datetime import datetime, timedelta
print(datetime.utcnow())
print(datetime(1970, 1, 1) + timedelta(seconds=time.time()))
print(datetime(*time.gmtime()[:6]))
Here's (non-tested) code that calls GetSystemTimeAsFileTime()on Windows based on CPython source:
这是基于 CPython 源GetSystemTimeAsFileTime()在 Windows上调用的（未经测试的）代码：
#!/usr/bin/env python
import ctypes.wintypes
from datetime import datetime, timedelta
def utcnow_microseconds():
system_time = ctypes.wintypes.FILETIME()
ctypes.windll.kernel32.GetSystemTimeAsFileTime(ctypes.byref(system_time))
large = (system_time.dwHighDateTime << 32) + system_time.dwLowDateTime
return large // 10 - 11644473600000000
print(datetime(1970, 1, 1) + timedelta(microseconds=utcnow_microseconds()))
Here's code that calls clock_gettime()on Python 2.
这是调用clock_gettime()Python 2的代码。
回答by markling
Problem only occurs with utc time (Python3).
问题只发生在 UTC 时间（Python3）。
e.g. System time:
例如系统时间：
$ date
Wed Jul 15 10:44:26 BST 2015
Python time correct when using datetime.now():
使用 datetime.now() 时 Python 时间正确：
>>> datetime.now()
datetime.datetime(2015, 7, 15, 10, 44, 30, 775840)
...But incorrect by one hour when using datetime.utcnow():
...但在使用 datetime.utcnow() 时一小时不正确：
>>> datetime.utcnow()
datetime.datetime(2015, 7, 15, 9, 44, 32, 599823)
UTC's problem is it doesn't know my timezone.
UTC 的问题是它不知道我的时区。
You have to tell it, with the help of a timezone module called pytz:
您必须在名为 pytz 的时区模块的帮助下告诉它：
>>> import pytz
>>> mytz = pytz.timezone('Europe/London')
>>> pytz.utc.localize(datetime.utcnow(), is_dst=None).astimezone(mytz)
datetime.datetime(2015, 7, 15, 11, 3, 43, 688681, tzinfo=<DstTzInfo 'Europe/London' BST+1:00:00 DST>)
References:
参考：
pytz - Converting UTC and timezone to local time
http://sweemengs-tech-world.blogspot.co.uk/2010/05/get-correct-datetime-value-for-python.html
http://sweemengs-tech-world.blogspot.co.uk/2010/05/get-correct-datetime-value-for-python.html
回答by Pramit Sood
I know I am tremendously late in replying to this.
我知道我回答这个问题太晚了。
I have tried doing this recently and therefore I suggest using datetime.now()instead of datetime.utcnow(). For my simple application that works fine.
我最近尝试过这样做，因此我建议使用datetime.now()而不是datetime.utcnow(). 对于我工作正常的简单应用程序。
回答by matkes
I know I'm five years late, but I had the same problem tonight. In my experience, the solution to the problem was to use the aware UTC datetime:
我知道我迟到了五年，但今晚我遇到了同样的问题。根据我的经验，问题的解决方案是使用感知 UTC 日期时间：
utc_dt_aware = datetime.datetime.now(datetime.timezone.utc)
If you google "utcnow() wrong" this is the first result you get, so I thought it would be good to answer anyway.
如果你用谷歌搜索“utcnow() 错误”，这是你得到的第一个结果，所以我认为无论如何回答都会很好。
