And if you want to stick to modules that are included in the Perl core (so no trip to CPAN), you can accomplish this with Time::Local's timelocal and POSIX's fab-oo strftime ...

use Time::Local;
use POSIX qw/ strftime /;

my $today     = '10/24/2000';

my $days_ago  = 1;

my $yesterday = do {

    my($m,$d,$y)  = split( m'/' => $today );

      # I use 12 as the hour here, so there's no 
      # confusion about daylight savings.

    my $t  = timelocal( 0, 0, 12, $d, $m - 1, $y - 1900 );
       $t -= $days_ago * 24*60*60 ;

    strftime( '%m/%d/%Y' => localtime($t) );
};

print "$today $yesterday";

[download]

Looks a lot like the Time::Piece (alt.) example, no? :)

    --k.


In reply to Re: Calculating 1-day-before by Kanji
in thread Calculating 1-day-before by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.