$refvalues=
[['1', '2008-04-04 17:30:01'],
....
['1', '2008-04-04 22:10:02']];

sub calcdiff
{
  ($d1, $d2) = @_;
  return ???
}

$is_in_state_0 = 0;
$start_date = '';
$end_date = '';
for(@$refvalues)
{
	if($is_in_state_0)
	{
		if($$_[0] eq '1')
		{
			$end_date = $$_[1];
			$is_in_state_0 = 0;
			print 'status 0 detected between '.$start_date.' and '.$end_date.' => '. calcdiff($start_date, $end_date)."\n"
		}	
	}
	else
	{
		if($$_[0] eq '0')
		{
			$is_in_state_0 = 1;
			$start_date = $$_[1];
		}
	}
}