use the DateTime module, sample/working code is below.

use strict;
use warnings;
use DateTime;

my $time = DateTime->new( month => 1, day => 21, year => 2008);
   $time->add( days => 45 );

print _option( $time->mdy(q{/}) );
for (1..45) {
  $time->subtract( days => 1 );
  print _option( $time->mdy(q{/}) );
}

sub _option {
  my $time = shift;

  return qq{<option value="$time">$time</option>\n}
}
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