grinder has asked for the wisdom of the Perl Monks concerning the following question:

Fellow monks,

I am hacking some Win32 OLE, and I'm having trouble formatting dates. Consider the following code (error checking omitted for clarity -- you may assume everything is working correctly):

  my $value = $obj->method_call();
  if( ref($value) eq 'Win32::OLE::Variant' and $value->Type == VT_DATE
+) {
    return $value->Date( 'yyyy/MM/dd' );
  }
  return $value;

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This will return, e.g. were this the date of this node, '2001/09/03'. Unfortunately, my problem is that I can't coax it to print out the hours, minutes and seconds. I am certain that the dates in question have sub-day components because the native application can display them -- it's Lotus Notes if you really care.

Win32::OLE::Variant does define a number of boilerplate styles for formatting dates, such as DATE_LONGDATE, which would spit out Monday, September 03, 2001. For finer control, you can also build up format strings (as per my example) from such building blocks as

There is also a Time() for formatting Win32::OLE::Variant objects as times, and it offers various ways of specifying hours, minutes and seconds.

The really frustrating part is that you can't use Date()'s format specifiers in Time() and vice versa. That is, the following doesn't work: 

  my $datestamp = $value->Date( 'yyyy/MM/dd hh:mm:ss' );

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(the 'hh:mm:ss' is passed through untouched).

In some ways this whole issue is moot, because what I would really like to do would be to convert the whole mess in epoch seconds and be done with it. That way the client code could format the date in a zillion different ways through other Perl modules (Date::Format springs to mind...).

But if I have little idea of how to format W::O::V dates, I have even less idea of how to get at the underlying representation to try and convert that to epoch time. Any clues I can use would be much appreciated.

--
g r i n d e r

Replies are listed 'Best First'.
Re: Formatting Win32::OLE::Variant Dates
by Corion (Patriarch) on Sep 04, 2001 at 00:27 UTC

    From the dark recesses of my mind creeps the following information :

    The OLE Variant Datetime is in fact a floating point number, whose integer part denotes the number of days since 31/12/1899, and whose fractional part denotes the part of a day.

    So you could try to coax the Variant into a number, and either concatenate $value->Date() and $value->Time() in the hope that Time() only looks at the fractional part, or use that fractional number and convert it into seconds since the epoch by subtracting the number of days between 12/31/1899 and 31/12/1969 from it and some more date trickery.

    Of course, the date range of the Variant is much higher than the number of seconds since the epoch, but your program won't be in use 2038 anyway, no ?

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      Well of course not! 2038 is unbelievably so far off in the future it will never happen.

      I will of course be living out my retirement at that point, so of course I wash my hands of the whole affair... besides all these young programmers need something to occupy themselves.

      Seriously though, I took your idea and played around a bit and came up with the following:

      #! /usr/bin/perl -w
use strict;
use Win32::OLE::Variant;
use Win32::OLE::NLS qw/ :LOCALE :DATE /;

my $v = Win32::OLE::Variant->new(VT_DATE, shift || 'Sep 3,2001');
print $v->Date( 'yyyy/MM/dd' ), "\n";
print $v->Number( {ThousandSep => '', DecimalSep => '.'}), "\n";

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      plugging in some values, we get:

      E:\david\perl>perl wov.pl "Sep 3,2001"
2001/09/03
37137.00

E:\david\perl>perl wov.pl "Jan 1,1900"
1900/01/01
2.00

E:\david\perl>perl wov.pl "Jan 2,1900"
1900/01/02
3.00

E:\david\perl>perl wov.pl "Jan 3,1900"
1900/01/03
4.00

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      So it appears that it will be possible to coax this into an epoch value. Thanks for the pointer.

      update: it works. I'm not sure how I missed this first time around, because I did play with the Time method... As it turns out, the Date and Time methods don't display the value as a date or time, but rather, they display the date or time component of the value. This means that if you want to build up a reasonable timestamp, you merely have to do the following:

        my $t = $v->Date( 'yyyy/MM/dd ' ) . $v->Time( 'HH:mm:ss' );
      --
      g r i n d e r
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