Parsing date with timezone from an email?

Question

I am trying to retrieve date from an email. At first it's easy:

message = email.parser.Parser().parse(file)
date = message['Date']
print date

and I receive:

'Mon, 16 Nov 2009 13:32:02 +0100'

But I need a nice datetime object, so I use:

datetime.strptime('Mon, 16 Nov 2009 13:32:02 +0100', '%a, %d %b %Y %H:%M:%S %Z')

which raises ValueError, since %Z isn't format for +0100. But I can't find proper format for timezone in the documentation, there is only this %Z for zone. Can someone help me on that?

Answer 1

Use email.utils.parsedate_tz(date):

msg=email.message_from_file(open(file_name))
date=None
date_str=msg.get('date')
if date_str:
    date_tuple=email.utils.parsedate_tz(date_str)
    if date_tuple:
        date=datetime.datetime.fromtimestamp(email.utils.mktime_tz(date_tuple))
if date:
    ... # valid date found

Answer 2

In Python 3.3+, email message can parse the headers for you:

import email
import email.policy

headers = email.message_from_file(file, policy=email.policy.default)
print(headers.get('date').datetime)
# -> 2009-11-16 13:32:02+01:00

Since Python 3.2+, it works if you replace %Z with %z:

>>> from datetime import datetime
>>> datetime.strptime("Mon, 16 Nov 2009 13:32:02 +0100", 
...                   "%a, %d %b %Y %H:%M:%S %z")
datetime.datetime(2009, 11, 16, 13, 32, 2,
                  tzinfo=datetime.timezone(datetime.timedelta(0, 3600)))

Or using email package (Python 3.3+):

>>> from email.utils import parsedate_to_datetime
>>> parsedate_to_datetime("Mon, 16 Nov 2009 13:32:02 +0100")
datetime.datetime(2009, 11, 16, 13, 32, 2,
                  tzinfo=datetime.timezone(datetime.timedelta(0, 3600)))

if UTC offset is specified as -0000 then it returns a naive datetime object that represents time in UTC otherwise it returns an aware datetime object with the corresponding tzinfo set.

To parse rfc 5322 date-time string on earlier Python versions (2.6+):

from calendar import timegm
from datetime import datetime, timedelta, tzinfo
from email.utils import parsedate_tz

ZERO = timedelta(0)
time_string = 'Mon, 16 Nov 2009 13:32:02 +0100'
tt = parsedate_tz(time_string)
#NOTE: mktime_tz is broken on Python < 2.7.4,
#  see https://bugs.python.org/issue21267
timestamp = timegm(tt) - tt[9] # local time - utc offset == utc time
naive_utc_dt = datetime(1970, 1, 1) + timedelta(seconds=timestamp)
aware_utc_dt = naive_utc_dt.replace(tzinfo=FixedOffset(ZERO, 'UTC'))
aware_dt = aware_utc_dt.astimezone(FixedOffset(timedelta(seconds=tt[9])))
print(aware_utc_dt)
print(aware_dt)
# -> 2009-11-16 12:32:02+00:00
# -> 2009-11-16 13:32:02+01:00

where FixedOffset is based on tzinfo subclass from the datetime documentation:

class FixedOffset(tzinfo):
    """Fixed UTC offset: `time = utc_time + utc_offset`."""
    def __init__(self, offset, name=None):
        self.__offset = offset
        if name is None:
            seconds = abs(offset).seconds
            assert abs(offset).days == 0
            hours, seconds = divmod(seconds, 3600)
            if offset < ZERO:
                hours = -hours
            minutes, seconds = divmod(seconds, 60)
            assert seconds == 0
            #NOTE: the last part is to remind about deprecated POSIX
            #  GMT+h timezones that have the opposite sign in the
            #  name; the corresponding numeric value is not used e.g.,
            #  no minutes
            self.__name = '<%+03d%02d>GMT%+d' % (hours, minutes, -hours)
        else:
            self.__name = name
    def utcoffset(self, dt=None):
        return self.__offset
    def tzname(self, dt=None):
        return self.__name
    def dst(self, dt=None):
        return ZERO
    def __repr__(self):
        return 'FixedOffset(%r, %r)' % (self.utcoffset(), self.tzname())

Answer 3

# Parses Nginx' format of "01/Jan/1999:13:59:59 +0400"
# Unfortunately, strptime doesn't support %z for the UTC offset (despite what
# the docs actually say), hence the need # for this function.
def parseDate(dateStr):
    date = datetime.datetime.strptime(dateStr[:-6], "%d/%b/%Y:%H:%M:%S")
    offsetDir = dateStr[-5]
    offsetHours = int(dateStr[-4:-2])
    offsetMins = int(dateStr[-2:])
    if offsetDir == "-":
        offsetHours = -offsetHours
        offsetMins = -offsetMins
    return date + datetime.timedelta(hours=offsetHours, minutes=offsetMins)

Answer 4

For python 3 you can use parsedate_to_datetime function:

>>> from email.utils import parsedate_to_datetime
>>> parsedate_to_datetime('Mon, 16 Nov 2009 13:32:02 +0100')
...
datetime.datetime(2009, 11, 16, 13, 32, 2, tzinfo=datetime.timezone(datetime.timedelta(0, 3600)))

Answer 5

Have you tried

rfc822.parsedate_tz(date) # ?

More on RFC822, http://docs.python.org/library/rfc822.html

It's deprecated (parsedate_tz is now in email.utils.parsedate_tz), though.

But maybe these answers help:

• How to parse dates with -0400 timezone string in python?

• python time to age part 2, timezones

Answer 6

email.utils has a parsedate() function for the RFC 2822 format, which as far as I know is not deprecated.

>>> import email.utils
>>> import time
>>> import datetime
>>> email.utils.parsedate('Mon, 16 Nov 2009 13:32:02 +0100')
(2009, 11, 16, 13, 32, 2, 0, 1, -1)
>>> time.mktime((2009, 11, 16, 13, 32, 2, 0, 1, -1))
1258378322.0
>>> datetime.datetime.fromtimestamp(1258378322.0)
datetime.datetime(2009, 11, 16, 13, 32, 2)

Please note, however, that the parsedate method does not take into account the time zone and time.mktime always expects a local time tuple as mentioned here.

>>> (time.mktime(email.utils.parsedate('Mon, 16 Nov 2009 13:32:02 +0900')) ==
... time.mktime(email.utils.parsedate('Mon, 16 Nov 2009 13:32:02 +0100'))
True

So you'll still need to parse out the time zone and take into account the local time difference, too:

>>> REMOTE_TIME_ZONE_OFFSET = +9 * 60 * 60
>>> (time.mktime(email.utils.parsedate('Mon, 16 Nov 2009 13:32:02 +0900')) +
... time.timezone - REMOTE_TIME_ZONE_OFFSET)
1258410122.0