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

Hi Monks!

I need help or directions on how to get in Perl 5 days prior or whatever number of days from a date.
Let say if the date passed is 09/10/2007, give me all info between 09/10/2007 -5 days, no weekends. It should be between 09/10/2007 and 09/03/2007.

I have the values from the dates but now I need to find a formula on how to do this, here is the code with the date values using Perl.

my($sec, $min, $hour, $mday, $mon, $year, $wday, $yday) = localtime(ti
+me);
my $thishour = ('0','1','2','3','4','5','6','7','8','9','10','11','12'
+,'1','2','3','4','5','6','7','8','9','10','11','12') [(localtime) [2]
+];
my $thismonth = ('Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep'
+,'Oct','Nov','Dec')[(localtime)[4]];

my $thisday = ('Sunday','Monday','Tuesday','Wednesday','Thursday','Fri
+day','Saturday')[(localtime)[6]];
my $day_number = ('1','2','3','4','5','6','7')[(localtime)[6]];

$mon++;
$year += 1900;

#I'm having problems figuring out how to find the date five days from 
+today's date.

print "Today is $thisday, $thismonth, $mday, $year";

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Replies are listed 'Best First'.
Re: Prior Date
by suaveant (Parson) on Oct 02, 2007 at 20:08 UTC
    or use Date::Manip in Business Mode

                    - Ant
                    - Some of my best work - (1 2 3)

[reply]
Re: Prior Date
by perlfan (Parson) on Oct 02, 2007 at 20:04 UTC
[reply]
Re: Prior Date
by djp (Hermit) on Oct 03, 2007 at 05:52 UTC
    ++ to the suggestions above. The first rule about calculatiing dates is: Don't Do It. It's complex, and someone else has done all the work for you. Use the OS (e.g. via POSIX::mktime, which normalizes the supplied date info), or someone else's work via a CPAN module.
[reply]
Re: Prior Date
by andreas1234567 (Vicar) on Oct 03, 2007 at 06:16 UTC
    I echo djp: Don't Reinvent the wheel. Date and time calculations (e.g. month changes, leap years, timezones) is surprisingly difficult to get right. Don't let that prevent you from doing the exercise though. 
    $ perl -l
use strict;
use warnings;
use DateTime;
print DateTime->new( year => 2007, month => 9, day => 10)->subtract( d
+ays => 5 )->ymd();
__END__
2007-09-05

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    --
    Andreas
[reply]
[d/l]
      Except the OP specified no weekends... I looked briefly at DateTime but didn't see anything for business days... but there must be something.

                      - Ant
                      - Some of my best work - (1 2 3)

[reply]
        I have this, but I can't figure it ou how to pass the values for the dates using a variable, can anyone try that?

        #!/usr/bin/perl

use strict;
use CGI qw/:standard/;
use CGI::Carp qw(fatalsToBrowser);
use DBI;
use Date::Pcalc qw(:all);

print header();

my $s_date="2007,09,27";
my $e_date="2007,10,3";

my @range = &Delta_Business_Days($s_date,$e_date);

    foreach my $date (@range)
    {
        print Date_to_Text(@{$date}), "\n"; # It breaks here...
        print "**$date**<br>";
  }

sub Delta_Business_Days
  {
      my(@date1) = (@_)[0,1,2];
      my(@date2) = (@_)[3,4,5];
      my($minus,$result,$dow1,$dow2,$diff,$temp);

      $minus  = 0;
      $result = Delta_Days(@date1,@date2);
      if ($result != 0)
      {
          if ($result < 0)
          {
              $minus = 1;
              $result = -$result;
              $dow1 = Day_of_Week(@date2);
              $dow2 = Day_of_Week(@date1);
          }
          else
          {
              $dow1 = Day_of_Week(@date1);
              $dow2 = Day_of_Week(@date2);
          }
          $diff = $dow2 - $dow1;
          $temp = $result;
          if ($diff != 0)
          {
              if ($diff < 0)
              {
                  $diff += 7;
              }
              $temp -= $diff;
              $dow1 += $diff;
              if ($dow1 > 6)
              {
                  $result--;
                  if ($dow1 > 7)
                  {
                      $result--;
                  }
              }
          }
          if ($temp != 0)
          {
              $temp /= 7;
              $result -= ($temp << 1);
          }
      }
      if ($minus) { return -$result; }
      else        { return  $result; }

  }

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