use strict;
use warnings;
use DateTime::Format::Strptime;

my $parser =
  DateTime::Format::Strptime->new( pattern => '%m/%d/%Y' );
while (<DATA>) {
	my $dt = $parser->parse_datetime( $_ );
	print $dt->ymd();
}

__DATA__
3/1/2006 0:00:00
7/22/2007 0:00:00
12/1/2006 0:00:00
12/22/2007 0:00:00