Python将毫秒转换为datetime并返回

Python trouble converting milliseconds to datetime and back

所以我有两个函数可以将python datetime.datetime()对象转换为毫秒和毫秒。我不知道哪里出了问题。以下是我的工作内容：

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>>> import datetime
>>> def mil_to_date(mil):
"""date items from REST services are reported in milliseconds,
this function will convert milliseconds to datetime objects

Required:
mil -- time in milliseconds
"""
if mil == None:
return None
elif mil < 0:
return datetime.datetime.utcfromtimestamp(0) + datetime.timedelta(seconds=(mil/1000))
else:
return datetime.datetime.fromtimestamp(mil / 1000)

>>> def date_to_mil(date):
"""converts datetime.datetime() object to milliseconds

date -- datetime.datetime() object"""
if isinstance(date, datetime.datetime):
epoch = datetime.datetime.utcfromtimestamp(0)
return long((date - epoch).total_seconds() * 1000.0)

>>> mil = 1394462888000
>>> date = mil_to_date(mil)
>>> date
datetime.datetime(2014, 3, 10, 9, 48, 8) #this is correct
>>> d2m = date_to_mil(date)
>>> d2m
1394444888000L
>>> mil
1394462888000L
>>> date2 = mil_to_date(d2m)
>>> date2
datetime.datetime(2014, 3, 10, 4, 48, 8) #why did I lose 5 hours??

因为某种原因，我损失了5个小时。我忽略了一些明显的东西吗？还是我的一个或两个功能都有问题？