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

my $str = "03/13/2016 09:59:59";

my $strp = DateTime::Format::Strptime->new(
	pattern => '%m/%d/%Y %H:%M:%S',
	time_zone=>'UTC', on_error=>'croak');

my $dt = $strp->parse_datetime($str);

print $dt->strftime('%Y-%m-%d %H:%M:%S %Z')," is ",
	$dt->clone->set_time_zone('America/Los_Angeles')
	->strftime('%Y-%m-%d %H:%M:%S %Z'),"\n";

$dt->add(seconds=>1);

print $dt->strftime('%Y-%m-%d %H:%M:%S %Z')," is ",
	$dt->clone->set_time_zone('America/Los_Angeles')
	->strftime('%Y-%m-%d %H:%M:%S %Z'),"\n";

__END__

2016-03-13 09:59:59 UTC is 2016-03-13 01:59:59 PST
2016-03-13 10:00:00 UTC is 2016-03-13 03:00:00 PDT