如何获取“午夜”的 UTC 时间对于给定的时区？

发布于 2024-07-10 01:47:52 字数 481 浏览 10 评论 0原文

我现在能想到的最好的办法就是这个怪物：

>>> datetime.utcnow() \
...   .replace(tzinfo=pytz.UTC) \
...   .astimezone(pytz.timezone("Australia/Melbourne")) \
...   .replace(hour=0,minute=0,second=0,microsecond=0) \
...   .astimezone(pytz.UTC) \
...   .replace(tzinfo=None)
datetime.datetime(2008, 12, 16, 13, 0)

即，用英语，获取当前时间（UTC），将其转换为其他时区，将时间设置为午夜，然后转换回 UTC。

我不只是使用 now() 或 localtime() ，因为这将使用服务器的时区，而不是用户的时区。

我不禁觉得自己错过了一些东西，有什么想法吗？

原文

The best I can come up with for now is this monstrosity:

>>> datetime.utcnow() \
...   .replace(tzinfo=pytz.UTC) \
...   .astimezone(pytz.timezone("Australia/Melbourne")) \
...   .replace(hour=0,minute=0,second=0,microsecond=0) \
...   .astimezone(pytz.UTC) \
...   .replace(tzinfo=None)
datetime.datetime(2008, 12, 16, 13, 0)

I.e., in English, get the current time (in UTC), convert it to some other timezone, set the time to midnight, then convert back to UTC.

I'm not just using now() or localtime() as that would use the server's timezone, not the user's timezone.

I can't help feeling I'm missing something, any ideas?

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止于盛夏 2024-07-17 01:47:53

使用 dateutil.tz 比 pytz 更简单：

>>>import datetime
>>>import dateutil.tz
>>>midnight=(datetime.datetime
             .now(dateutil.tz.gettz('Australia/Melbourne'))
             .replace(hour=0, minute=0, second=0, microsecond=0)
             .astimezone(dateutil.tz.tzutc()))
>>>print(midnight)
2019-04-26 14:00:00+00:00

tzinfo 文档从 Python 3.6 开始推荐使用 dateutil.tz。 dateutil.tz 中的 tzinfo 对象没有像 DST 这样的异常问题，不需要 pytz 的本地化功能。使用 user3850 的示例：

>>> now = (datetime.datetime(2012, 4, 1, 5,  
...         tzinfo = dateutil.tz.gettz('Australia/Melbourne'))) 
>>> print(now.replace(hour = 0).astimezone(dateutil.tz.tzutc()))
2012-03-31 13:00:00+00:00

This is more straightforward with dateutil.tz than pytz:

>>>import datetime
>>>import dateutil.tz
>>>midnight=(datetime.datetime
             .now(dateutil.tz.gettz('Australia/Melbourne'))
             .replace(hour=0, minute=0, second=0, microsecond=0)
             .astimezone(dateutil.tz.tzutc()))
>>>print(midnight)
2019-04-26 14:00:00+00:00

The tzinfo documentation recommends dateutil.tz since Python 3.6. The tzinfo objects from dateutil.tz have no problems with anomalies like DST without requiring the localize functionality of pytz. Using the example from user3850:

>>> now = (datetime.datetime(2012, 4, 1, 5,  
...         tzinfo = dateutil.tz.gettz('Australia/Melbourne'))) 
>>> print(now.replace(hour = 0).astimezone(dateutil.tz.tzutc()))
2012-03-31 13:00:00+00:00

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中二柚 2024-07-17 01:47:53

设置 TZ 环境变量会修改 Python 的日期和时间函数使用的时区。

>>> time.gmtime()
(2008, 12, 17, 1, 16, 46, 2, 352, 0)
>>> time.localtime()
(2008, 12, 16, 20, 16, 47, 1, 351, 0)
>>> os.environ['TZ']='Australia/Melbourne'
>>> time.localtime()
(2008, 12, 17, 12, 16, 53, 2, 352, 1)

Setting the TZ environment variable modifies what timezone Python's date and time functions work with.

>>> time.gmtime()
(2008, 12, 17, 1, 16, 46, 2, 352, 0)
>>> time.localtime()
(2008, 12, 16, 20, 16, 47, 1, 351, 0)
>>> os.environ['TZ']='Australia/Melbourne'
>>> time.localtime()
(2008, 12, 17, 12, 16, 53, 2, 352, 1)

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过潦 2024-07-17 01:47:53

每个时区都有一个数字，例如美国/中部= -6。这被定义为与 UTC 的小时偏移量。由于 0000 是午夜，因此您可以简单地使用此偏移量来查找任何时区中午夜 UTC 的时间。要访问它，我相信您可以使用

 time.timezone

根据 Python 文档， time.timezone 实际上给出了这个数字的负值：

<块引用>
时间.时区
<块引用>
本地（非 DST）时区的偏移量，以 UTC 以西的秒数为单位（西欧大部分地区为负值，美国为正值，英国为零）。

因此，如果该数字为正数，则只需使用该数字表示时间（以小时为单位）（即，如果芝加哥是午夜（时区值为 +6），则 6000 = UTC 时间上午 6 点）。

如果数字是负数，则从 24 中减去。例如，柏林会给出 -1，因此 24 - 1 => 2300 = 晚上 11 点。

Each time zone has a number, eg US/Central = -6. This is defined as the offset in hours from UTC. Since 0000 is midnight, you can simply use this offset to find the time in any time zone when it is midnight UTC. To access that, I believe you can use

 time.timezone

According to The Python Docs, time.timezone actually gives the negative value of this number:

time.timezone
The offset of the local (non-DST) timezone, in seconds west of UTC (negative in most of Western Europe, positive in the US, zero in the UK).

So you would simply use that number for the time in hours if it's positive (i.e., if it's midnight in Chicago (which has a +6 timezone value), then it's 6000 = 6am UTC).

If the number is negative, subtract from 24. For example, Berlin would give -1, so 24 - 1 => 2300 = 11pm.

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放飞的风筝 2024-07-17 01:47:53

值得一提的是，我们可以调整 @jfs 给出的答案来查找明天的午夜或昨天的午夜等。诀窍是向感知时区添加一定的天数。这是有效的，因为虽然这通常会增加 24 小时，但有时可能会根据 DST 问题增加 23 或 25 小时。

from datetime import datetime, time, timedelta
import pytz

def midnight_UTC(offset):

    # Construct a timezone object
    tz = pytz.timezone('Australia/Melbourne')

    # Work out today/now as a timezone-aware datetime
    today = datetime.now(tz)

    # Adjust by the offset. Note that that adding 1 day might actually move us 23 or 25
    # hours into the future, depending on daylight savings. This works because the {today}
    # variable is timezone aware
    target_day = today + timedelta(days=1) * offset

    # Discard hours, minutes, seconds and microseconds
    midnight_aware = tz.localize(
        datetime.combine(target_day, time(0, 0, 0, 0)), is_dst=None)

    # Convert to UTC
    midnight_UTC = midnight_aware.astimezone(pytz.utc)

    return midnight_UTC

print("The UTC time of the previous midnight is:", midnight_UTC(0))
print("The UTC time of the upcoming midnight is:", midnight_UTC(1))

It's worth remarking that we can adapt the answer given by @jfs to find tomorrow's midnight or yesterday's midnight, etc. The trick is to add a certain number of days to the aware timezone. This works because although this usually adds 24 hours, sometimes it might add 23 or 25 based on DST issues.

from datetime import datetime, time, timedelta
import pytz

def midnight_UTC(offset):

    # Construct a timezone object
    tz = pytz.timezone('Australia/Melbourne')

    # Work out today/now as a timezone-aware datetime
    today = datetime.now(tz)

    # Adjust by the offset. Note that that adding 1 day might actually move us 23 or 25
    # hours into the future, depending on daylight savings. This works because the {today}
    # variable is timezone aware
    target_day = today + timedelta(days=1) * offset

    # Discard hours, minutes, seconds and microseconds
    midnight_aware = tz.localize(
        datetime.combine(target_day, time(0, 0, 0, 0)), is_dst=None)

    # Convert to UTC
    midnight_UTC = midnight_aware.astimezone(pytz.utc)

    return midnight_UTC

print("The UTC time of the previous midnight is:", midnight_UTC(0))
print("The UTC time of the upcoming midnight is:", midnight_UTC(1))

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清旖 2024-07-17 01:47:52

我认为如果你这样做的话，你可以减少一些方法调用：

>>> from datetime import datetime
>>> datetime.now(pytz.timezone("Australia/Melbourne")) \
            .replace(hour=0, minute=0, second=0, microsecond=0) \
            .astimezone(pytz.utc)

但是......你的代码中有一个比美观更大的问题：它会在切换到夏令时或从夏令时切换到夏令时的那天给出错误的结果。

原因是日期时间构造函数和 replace() 都没有考虑 DST 更改。

例如：

>>> now = datetime(2012, 4, 1, 5, 0, 0, 0, tzinfo=pytz.timezone("Australia/Melbourne"))
>>> print now
2012-04-01 05:00:00+10:00
>>> print now.replace(hour=0)
2012-04-01 00:00:00+10:00 # wrong! midnight was at 2012-04-01 00:00:00+11:00
>>> print datetime(2012, 3, 1, 0, 0, 0, 0, tzinfo=tz)
2012-03-01 00:00:00+10:00 # wrong again!

但是，tz.localize() 的文档指出：

此方法应该用于构造本地时间，而不是
而不是将 tzinfo 参数传递给日期时间构造函数。

因此，你的问题是这样解决的：

>>> import pytz
>>> from datetime import datetime, date, time

>>> tz = pytz.timezone("Australia/Melbourne")
>>> the_date = date(2012, 4, 1) # use date.today() here

>>> midnight_without_tzinfo = datetime.combine(the_date, time())
>>> print midnight_without_tzinfo
2012-04-01 00:00:00

>>> midnight_with_tzinfo = tz.localize(midnight_without_tzinfo)
>>> print midnight_with_tzinfo
2012-04-01 00:00:00+11:00

>>> print midnight_with_tzinfo.astimezone(pytz.utc)
2012-03-31 13:00:00+00:00

不过，不能保证 1582 年之前的日期。

I think you can shave off a few method calls if you do it like this:

>>> from datetime import datetime
>>> datetime.now(pytz.timezone("Australia/Melbourne")) \
            .replace(hour=0, minute=0, second=0, microsecond=0) \
            .astimezone(pytz.utc)

BUT… there is a bigger problem than aesthetics in your code: it will give the wrong result on the day of the switch to or from Daylight Saving Time.

The reason for this is that neither the datetime constructors nor replace() take DST changes into account.

For example:

>>> now = datetime(2012, 4, 1, 5, 0, 0, 0, tzinfo=pytz.timezone("Australia/Melbourne"))
>>> print now
2012-04-01 05:00:00+10:00
>>> print now.replace(hour=0)
2012-04-01 00:00:00+10:00 # wrong! midnight was at 2012-04-01 00:00:00+11:00
>>> print datetime(2012, 3, 1, 0, 0, 0, 0, tzinfo=tz)
2012-03-01 00:00:00+10:00 # wrong again!

However, the documentation for tz.localize() states:

This method should be used to construct localtimes, rather
than passing a tzinfo argument to a datetime constructor.

Thus, your problem is solved like so:

>>> import pytz
>>> from datetime import datetime, date, time

>>> tz = pytz.timezone("Australia/Melbourne")
>>> the_date = date(2012, 4, 1) # use date.today() here

>>> midnight_without_tzinfo = datetime.combine(the_date, time())
>>> print midnight_without_tzinfo
2012-04-01 00:00:00

>>> midnight_with_tzinfo = tz.localize(midnight_without_tzinfo)
>>> print midnight_with_tzinfo
2012-04-01 00:00:00+11:00

>>> print midnight_with_tzinfo.astimezone(pytz.utc)
2012-03-31 13:00:00+00:00

No guarantees for dates before 1582, though.

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唐婉 2024-07-17 01:47:52

@hop 的答案在从夏令时 (DST) 过渡的那天是错误的，例如 2012 年 4 月 1 日。要修复它 tz.localize() 可以使用：

tz = pytz.timezone("Australia/Melbourne")
today = datetime.now(tz).date()
midnight = tz.localize(datetime.combine(today, time(0, 0)), is_dst=None)
utc_dt = midnight.astimezone(pytz.utc)

与注释相同：

#!/usr/bin/env python
from datetime import datetime, time
import pytz # pip instal pytz

tz = pytz.timezone("Australia/Melbourne") # choose timezone

# 1. get correct date for the midnight using given timezone.
today = datetime.now(tz).date()

# 2. get midnight in the correct timezone (taking into account DST)
#NOTE: tzinfo=None and tz.localize()
# assert that there is no dst transition at midnight (`is_dst=None`)
midnight = tz.localize(datetime.combine(today, time(0, 0)), is_dst=None)

# 3. convert to UTC (no need to call `utc.normalize()` due to UTC has no 
#    DST transitions)
fmt = '%Y-%m-%d %H:%M:%S %Z%z'
print midnight.astimezone(pytz.utc).strftime(fmt)

@hop's answer is wrong on the day of transition from Daylight Saving Time (DST) e.g., Apr 1, 2012. To fix it tz.localize() could be used:

tz = pytz.timezone("Australia/Melbourne")
today = datetime.now(tz).date()
midnight = tz.localize(datetime.combine(today, time(0, 0)), is_dst=None)
utc_dt = midnight.astimezone(pytz.utc)

The same with comments:

#!/usr/bin/env python
from datetime import datetime, time
import pytz # pip instal pytz

tz = pytz.timezone("Australia/Melbourne") # choose timezone

# 1. get correct date for the midnight using given timezone.
today = datetime.now(tz).date()

# 2. get midnight in the correct timezone (taking into account DST)
#NOTE: tzinfo=None and tz.localize()
# assert that there is no dst transition at midnight (`is_dst=None`)
midnight = tz.localize(datetime.combine(today, time(0, 0)), is_dst=None)

# 3. convert to UTC (no need to call `utc.normalize()` due to UTC has no 
#    DST transitions)
fmt = '%Y-%m-%d %H:%M:%S %Z%z'
print midnight.astimezone(pytz.utc).strftime(fmt)

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