Re: [mdb-dev] mdb-export and no dates become 1970

[David W. <dav...@ya...>]

Hi Jeff,

 --- Jeff Smith <why...@ya...> wrote: 
> David,
> 
> First, here is a little background info, FWIW.  In
> an MDB,
> date/time info is stored as a 'double' containing
> the
> number days from 12/30/1899.  Internally there is no
> distinction between 6:00 and 12/30/1899 6:00 (0.25).
> I believe information on how to format the output in
> Access is stored elsewhere in the MDB.  Try
> exporting
> a table with a date-less time from Access to a text
> file
> and you will see a date with it there too.

Gotcha. 


> mdbtools has been using gmtime to populate a 'tm'
> structure.
> That only really works for 'unix time' though (1970
> - 2038).
> I am looking at ways to populate it that would work
> for dates
> from 1/1/100 to 12/31/9999, as Access allows.  This
> would
> still have the same issue with exporting as Access
> does.  But
> maybe 1899 would be more acceptable in your case
> than 1970.

Currently I don't have a specific problem, I am trying
to think ahead and anticipate problems that might crop
up. 1899 will probably be less common than 1970, so
this should help. I will add a note (based on your
comments if that's okay) warning users about times
without dates.

> 
> BTW, with mdb-export you can use -D to set the
> output format,
> but this will be applied to the whole table, which
> is probably
> not what you had in mind.

Yes, I use this to make sure the dates/times come out
in a standard format. I think I'll add an option to
change the default that I use.

Thanks for your help.

Dave

> 
>  -- Jeff Smith
> 
> 
> --- David Whiting <dav...@ya...> wrote:
> > Hi,
> > 
> > I am playing with developing some wrappers to use
> > mdbtools with a statistical package
> > (www.r-project.org). I notice that mdb-export will
> > export data stored as Date/Time type that only
> contain
> > the time component with the default date of
> > 01/01/1970. This means that it will not be
> possible
> > for me to distinguish between real dates of
> 01/01/1970
> > and times with missing dates. Is there any way to
> > distinguish between the two, or is this a
> limitation
> > of the way access stores the data in the first
> place? 
> > 
> > Dave
> 
> 
> 
> 
> 		
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