[egenix-users] Parsing ARPA dates before Unix epoch breaks?

[Ramon Felciano]

Never mind, I just noticed that the str() function has an optional
timezone parameter, so the following seems to work:

>>> s = "Wed, 1 Jan 1969 00:43:25 -0400"
>>> delta = ParseDateTime(s) - ParseDateTimeUTC(s)
Traceback (most recent call last):
  File "<interactive input>", line 1, in <module>
NameError: name 'ParseDateTime' is not defined
>>> delta = mx.DateTime.ARPA.ParseDateTime(s) - mx.DateTime.ARPA.ParseDateTimeUTC(s)
>>> mx.DateTime.ARPA.str(mx.DateTime.ARPA.ParseDateTime(s), delta)
'Wed, 01 Jan 1969 00:43:25 -0400'
>>>

Thanks!

Ramon

On Fri, Apr 16, 2010 at 3:20 PM, Ramon Felciano <felciano at yahoo.com> wrote:
> (RESEND: Sorry, meant to CC the list on this as well...)
>
> Hi Marc --
>
> Thanks for the quick reply. Is there a way I can re-construct the
> original date (with time offset) such that it will be formatted
> correctly by the mxTimeDate str() function? I'm not actually calling
> gmtoffset() myself, but that's where the str function seems to choke:
>
>>>> from mx.DateTime.ARPA import *
>>>> s = "Wed, 1 Jan 1969 00:43:25 -0400"
>>>> delta = ParseDateTime(s) - ParseDateTimeUTC(s)
>>>> delta
> <mx.DateTime.DateTimeDelta object for '-04:00:00.00' at 1363840>
>>>> ParseDateTime(s) + delta
> <mx.DateTime.DateTime object for '1968-12-31 20:43:25.00' at 1369be0>
>>>> str(ParseDateTime(s) + delta)
> Traceback (most recent call last):
>  File "<interactive input>", line 1, in <module>
>  File "C:\Python26\lib\site-packages\mx\DateTime\ARPA.py", line 170, in str
>    tz = datetime.gmtoffset()
> Error: cannot convert value to a time value
>>>>
>
> Thanks,
>
> Ramon
>
>> On Thu, Apr 15, 2010 at 4:07 PM, M.-A. Lemburg <mal at egenix.com> wrote:
>>> Ramon Felciano wrote:
>>>> Hi --
>>>>
>>>> I've run into trouble parsing dates using the ARPA module in
>>>> mxDateTime on Windows. It appears that it is based on a limitation
>>>> around dates before the Unix epoch, which I thought this package
>>>> helped you work around:
>>>>
>>>>>>> mx.__version__
>>>> '3.1.2'
>>>>>>> mx.DateTime.ARPA.ParseDateTimeUTC("Thu, 1 Jan 1970 00:43:25 -0400").gmtoffset()
>>>> <mx.DateTime.DateTimeDelta object for '-08:00:00.00' at 1497b60>
>>>>>>> mx.DateTime.ARPA.ParseDateTimeUTC("Wed, 1 Jan 1969 00:43:25 -0400").gmtoffset()
>>>> Traceback (most recent call last):
>>>>   File "<interactive input>", line 1, in <module>
>>>> Error: cannot convert value to a time value
>>>>
>>>> Is this expected behavior?
>>>
>>> Yes, since the .gmtoffset() method uses the C lib's time function
>>> in order to calculate the offset of the object's date/time
>>> to GMT/UTC, provided that the object uses local time.
>>>
>>> On some systems, this fails for dates prior to the epoch and there's
>>> nothing much we can do about it.
>>>
>>> On others it works just fine, e.g. Linux:
>>>
>>>>>> ParseDateTime("Wed, 1 Jan 1969 00:43:25").gmtoffset()
>>> <mx.DateTime.DateTimeDelta object for '01:00:00.00' at 2b46aebfac70>
>>>>>> ParseDateTime("Wed, 1 Jan 1960 00:43:25").gmtoffset()
>>> <mx.DateTime.DateTimeDelta object for '01:00:00.00' at 2b46aec16b58>
>>>>>> ParseDateTime("Wed, 1 Jan 1920 00:43:25").gmtoffset()
>>> <mx.DateTime.DateTimeDelta object for '01:00:00.00' at 2b46aebfac70>
>>>>>> ParseDateTime("Wed, 1 Jan 1910 00:43:25").gmtoffset()
>>> <mx.DateTime.DateTimeDelta object for '01:00:00.00' at 2b46aec16b58>
>>>>>> ParseDateTime("Wed, 1 Jan 1810 00:43:25").gmtoffset()
>>> <mx.DateTime.DateTimeDelta object for '00:53:28.00' at 2b46aebfac70>
>>>>>> ParseDateTime("Wed, 1 Jan 1710 00:43:25").gmtoffset()
>>> <mx.DateTime.DateTimeDelta object for '00:53:28.00' at 2b46aec16b58>
>>>
>>> Also note that ParseDateTimeUTC("Wed, 1 Jan 1969 00:43:25 -0400")
>>> will return a DateTime instance pointing to UTC time, ie. the
>>> .gmtoffset() is not applicable.
>>>
>>> You can use ParseDateTime("Wed, 1 Jan 1969 00:43:25 -0400") to
>>> get the date/time parsed without the timezone part and then
>>> take the difference to extract the already provided timezone
>>> information:
>>>
>>>>>> from mx.DateTime.ARPA import *
>>>>>> offset = ParseDateTime("Wed, 1 Jan 1969 00:43:25 -0400") - ParseDateTimeUTC("Wed, 1 Jan 1969
>>> 00:43:25 -0400")
>>>>>> offset
>>> <mx.DateTime.DateTimeDelta object for '-04:00:00.00' at 2b46aec163b0>
>>>
>>> --
>>> Marc-Andre Lemburg
>>> eGenix.com
>>>
>>> Professional Python Services directly from the Source  (#1, Apr 16 2010)
>>>>>> Python/Zope Consulting and Support ...        http://www.egenix.com/
>>>>>> mxODBC.Zope.Database.Adapter ...             http://zope.egenix.com/
>>>>>> mxODBC, mxDateTime, mxTextTools ...        http://python.egenix.com/
>>> ________________________________________________________________________
>>>
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>>
>