我正在使用 Google App Engine，我了解到时区固定为 UTC。我想确定用户本地时区当天的开始和结束时间。所以基本上，给定 UTC 的当前时间，如何确定当天的开始和结束时间，同时考虑到夏令时转换。
我有一些笨重的示例代码。请注意，我意识到，如果我手动指定日期，我也可以指定明天的日期，但它们只是示例，我想以编程方式确定它。我的主要问题是，如果我将 timedelta 添加到带有时区的日期时间，然后将其标准化（就像 pytz 文档中建议的那样），我会得到一个在夏令时切换期间关闭一个小时的日期时间。
代码中未提及，但最终目标是将这些时间转换回 UTC，这就是为什么了解时区很重要。
#!/usr/bin/python
import datetime
from pytz.gae import pytz
hobart_tz = pytz.timezone('Australia/Hobart')
utc_dt = pytz.utc.localize(datetime.datetime.utcnow())
hobart_dt = utc_dt.astimezone(hobart_tz)
# create a new datetime for the start of the day and add a day to it to get tomorrow.
today_start = datetime.datetime(hobart_dt.year, hobart_dt.month, hobart_dt.day)
today_start = hobart_tz.localize(today_start)
today_end = hobart_tz.normalize(today_start + datetime.timedelta(days=1))
print 'today:', today_start
print ' next:', today_end
print
# gives:
# today: 2011-08-28 00:00:00+10:00
# next: 2011-08-29 00:00:00+10:00
# but say today is a daylight savings changeover.
# after normalisation, we are off by an hour.
dst_finish_2011 = datetime.datetime(2011, 4, 3) # this would come from hobart_dt
dst_finish_2011 = hobart_tz.localize(dst_finish_2011)
next = hobart_tz.normalize(dst_finish_2011 + datetime.timedelta(days=1))
print '2011-04-03:', dst_finish_2011
print '2011-04-04:', next # expect 2011-04-04 00:00:00+10:00
print
# gives
# 2011-04-03: 2011-04-03 00:00:00+11:00
# 2011-04-04: 2011-04-03 23:00:00+10:00 (wrong)
dst_start_2011 = datetime.datetime(2011, 10, 2) # this would come from hobart_dt
dst_start_2011 = hobart_tz.localize(dst_start_2011)
next = hobart_tz.normalize(dst_start_2011 + datetime.timedelta(days=1))
print '2011-10-02:', dst_start_2011
print '2011-10-03:', next # expect 2011-10-03 00:00:00+11:00
print
# gives
# 2011-10-02: 2011-10-02 00:00:00+10:00
# 2011-10-03: 2011-10-03 01:00:00+11:00 (wrong)
# I guess we could ignore the timezone and localise *after* ?
dst_finish_2011 = datetime.datetime(2011, 4, 3) # this would come from hobart_dt
next = dst_finish_2011 + datetime.timedelta(days=1)
# now localise
dst_finish_2011 = hobart_tz.localize(dst_finish_2011)
next = hobart_tz.localize(next)
print '2011-04-03:', dst_finish_2011
print '2011-04-04:', next # expect 2011-04-04 00:00:00+10:00
print
# gives
# 2011-04-03: 2011-04-03 00:00:00+11:00
# 2011-04-04: 2011-04-04 00:00:00+10:00
要找出当地时区当天的开始时间（午夜）和当天的结束时间（明天），并了解 UTC 时间：
#!/usr/bin/env python
from datetime import datetime, time, timedelta
import pytz # $ pip install pytz
from tzlocal import get_localzone # $ pip install tzlocal
tz = get_localzone() # get the local timezone as pytz.timezone
now = datetime.now(pytz.utc) # some UTC time
dt = now.astimezone(tz) # the same time in the local timezone
today = dt.date() # today in the local timezone (naive date object)
midnight = datetime.combine(today, time()) # midnight in the local timezone
aware_midnight = tz.localize(midnight, is_dst=None) # raise exception
# for ambiguous or
# non-existing
# times
tomorrow = midnight + timedelta(1)
aware_tomorrow = tz.localize(tomorrow, is_dst=None)
def print_time(aware_dt, fmt="%Y-%m-%d %H:%M:%S %Z%z"):
print(aware_dt.strftime(fmt))
utc_dt = aware_dt.astimezone(pytz.utc) # the same time in UTC
print(utc_dt.strftime(fmt))
print_time(aware_midnight)
print_time(aware_tomorrow)
2014-09-01 00:00:00 EST+1000
2014-08-31 14:00:00 UTC+0000
2014-09-02 00:00:00 EST+1000
2014-09-01 14:00:00 UTC+0000
另请参阅，
我相信您得到这个结果是因为您添加了一天而不是 86400 秒。天和秒之间不存在统一、始终正确的等价关系。例如，如果
pytz因此，添加一天意味着简单地将一天增加一天，如有必要，则延续到月份和年份，但不更改一天中的时间字段。尝试添加 86400 秒，看看是否得到所需的结果。
使用
arrowimport arrow
from datetime import date
def get_start_end_utc_of_date(date: date | str, timezone="UTC") -> tuple[arrow.Arrow, arrow.Arrow]:
specific_date = arrow.get(date)
day = specific_date.day
local_date = specific_date.to(timezone)
start_of_day_local = local_date.floor('day')
# If tz is negative, day floor will be the previous day, so we need to adjust it
start = start_of_day_local.replace(day=day)
return start, start.shift(days=1)
>>> print(get_start_end_utc_of_date("2024-03-15", "America/New_York"))
(<Arrow [2024-03-15T00:00:00-04:00]>, <Arrow [2024-03-16T00:00:00-04:00]>)
经过一些实验和思考，我相信我有一个适合您的解决方案。正如您指出的那样，我之前的回答并不正确； days=1 的 timedelta 对象与秒=86400 的 timedelta 对象基本相同（除了涉及闰秒的地方）。
我推荐的一种方法是使用
datetime.datedatetime.datetime>>> oneday = datetime.timedelta(days=1)
>>> d = datetime.date(2011,4,3)
>>> str(d + oneday)
'2011-04-04'
然后可以添加一天中的时间以形成一个完整的
datetime.datetime另一种我认为可以安全使用的方法是暂时使用“天真的”日期。这样，添加
timedelta>>> hob = pytz.timezone('Australia/Hobart')
>>> dstlast = datetime.datetime(2011,4,3)
>>> str(dstlast)
'2011-04-03 00:00:00'
>>> dstlasthob = hob.localize(dstlast)
>>> str(dstlasthob)
'2011-04-03 00:00:00+11:00'
>>> oneday = datetime.timedelta(days=1)
>>> str(hob.normalize(dstlasthob + oneday))
'2011-04-03 23:00:00+10:00'
>>> nextday = hob.localize(dstlasthob.replace(tzinfo=None) + oneday)
>>> str(nextday)
'2011-04-04 00:00:00+10:00'
我针对包含闰秒的日期测试了此方法（例如 2008-12-31），结果为一天中的时间 00:00:00。这实际上可能是错误的，我不确定，但这就是你想要的:-)
以下代码尝试获取午夜时间；如果时区调整失败，它会使用新的时区偏移量重新调整回午夜。
def DayStartEnd(localized_dt):
tz = localized_dt.tzinfo
start = tz.normalize(datetime.datetime(localized_dt.year,localized_dt.month,localized_dt.day,0,0,0,0,tz))
after_midnight = start.hour*60*60 + start.minute*60 + start.second
if start.day != localized_dt.day:
start += datetime.timedelta(seconds = 24*60*60 - after_midnight)
elif after_midnight != 0:
start -= datetime.timedelta(seconds = after_midnight)
end = tz.normalize(start + datetime.timedelta(hours=24))
after_midnight = end.hour*60*60 + end.minute*60 + end.second
if end.day == localized_dt.day:
end += datetime.timedelta(seconds = 24*60*60 - after_midnight)
elif after_midnight != 0:
end -= datetime.timedelta(seconds = after_midnight)
return start,end
>>> hobart_tz = pytz.timezone('Australia/Hobart')
>>> dst_finish_2011 = datetime.datetime(2011, 4, 3)
>>> dst_finish_2011 = hobart_tz.localize(dst_finish_2011)
>>> start,end = DayStartEnd(dst_finish_2011)
>>> print start,end
2011-04-03 00:00:00+11:00 2011-04-04 00:00:00+10:00
>>> dst_start_2011 = datetime.datetime(2011, 10, 2)
>>> dst_start_2011 = hobart_tz.localize(dst_start_2011)
>>> start,end = DayStartEnd(dst_start_2011)
>>> print start,end
2011-10-02 00:00:00+10:00 2011-10-03 00:00:00+11:00