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Re: Problem parsing date formats using Import

  • To: mathgroup at smc.vnet.net
  • Subject: [mg90508] Re: [mg90458] Problem parsing date formats using Import
  • From: Curtis Osterhoudt <cfo at lanl.gov>
  • Date: Fri, 11 Jul 2008 02:03:59 -0400 (EDT)
  • Organization: LANL
  • References: <200807101033.GAA15271@smc.vnet.net>
  • Reply-to: cfo at lanl.gov

Hi, Jon, 

   If a date like 20080101 gives you something like {1900, 8, 21, 9, 48, 21.} 
that's because Mathematica is treating the original number as the number of 
seconds since Jan 01, 1900. 

   I usually, if I have a consistent format of dates, prefer to write a 
parsing function myself -- it's usually much faster than relying on 
Mathematica. The program has to figure out if something is a date, and then 
figure out what the format is (heuristically?) and then do the translation. 
And, so far as I know, it has to do this on every number it encounters in a 
long list of dates. Slow!

   If you still want to have Mathematica parse dates like 20080101 as Jan 01, 
2008, then turn them into strings! 
 
In[28]:= DateList["20080101"]

Out[28]= {2008, 1, 1, 0, 0, 0.}

                Best wishes, 
                            C.O.

On Thursday 10 July 2008 04:33:43 Jon wrote:
> Hi,
>
> I'm trying to parse a file which has dates in the format YYYYMMDD,
> e.g. 20080101. However I just can't seem to get the DateStringFormat
> to work - it works fine for YYYY-MM-DD or YYYYMM-DD but not if I
> remove the separators entirely. Is this because of the ambiguity
> between numeric and this date format? Does the automatic date parsing
> not work for entirely numeric date formats?
>
> Thanks and regards,
> Jon Rowland
>
> In[137]:= ImportString["1982-04-22\n1982-04-23", "Table",
> "DateStringFormat" -> {"Year", "-", "Month", "-", "Day"}]
> Out[137]= {{{1982, 4, 22}}, {{1982, 4, 23}}}
>
> In[138]:= ImportString["198204-22\n198204-23", "Table",
> "DateStringFormat" -> {"Year", "Month", "-", "Day"}]
> Out[138]= {{{1982, 4, 22}}, {{1982, 4, 23}}}
>
> In[139]:= ImportString["19820422\n19820423", "Table",
> "DateStringFormat" -> {"Year", "Month", "Day"}]
> Out[139]= {{19820422}, {19820423}}



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