Untitled

SELECT label_a.start_date, (SELECT min(end_date) from projects label_b WHERE label_b.end_date NOT IN (SELECT start_date from projects) AND label_b.end_date > label_a.start_date) 
AS x FROM projects label_a
WHERE label_a.start_date 
NOT IN (SELECT end_date FROM projects) 
ORDER BY x - label_a.start_date, label_a.start_date;