#!/usr/bin/perl -w
use strict;

use Date::Calc ( ":all" );
use Date::Manip;

my ( $date, $yy, $dd, $mm );

print "There are various ways to get yesterday's date.  Here are\n",
      "are a few alternatives and their results:\n\n";

# perlfaq4 - simple

$date = scalar localtime( ( time() - ( 24 * 60 * 60 ) ) );
print "1. The simple calculation in perlfaq4 yields: ",
      "$date.\n\n";


# perlfaq4 - DST aware

$date = scalar localtime( yesterday() );
print "2. The DST subroutine in perlfaq4 reports: ",
      "$date.\n\n";


# One way using Date::Calc

( $yy, $mm, $dd ) = Today();
( $yy, $mm, $dd ) = Add_Delta_Days( $yy, $mm, $dd, -1 );
$mm = Month_to_Text( $mm );
print "3. A simple use of Date::Calc gives: ",
      "$dd $mm $yy.\n\n";


# Date::Manip; note that the timezone is my local;
# change as needed.

$ENV{TZ} = "PST8PDT";
$date = ParseDate( "yesterday" );

print "4. Date::Manip returns $date, as well as ",
      UnixDate( "yesterday", "%e %b %Y"),
      "\n\n";


print "Other approaches are certainly possible.\n";
exit 1;


sub yesterday
{ # Borrowed from perlfaq4; note changes below.
  my $now  = defined $_[0] ? $_[0] : time;
  my $then = $now - 60 * 60 * 24;
  my $ndst = (localtime $now)[8] > 0;
  my $tdst = (localtime $then)[8] > 0;

  # Added '=' to avoid warning (and return)
  $then -= ($tdst - $ndst) * 60 * 60;
  return $then
}