forming a habit habit forming studies have thoroughly debunked the 21-day myth The Huffington Post it takes three months to form a new habit. studies have thoroughly debunked the 21-day myth it takes 66 days to create a habit, it takes about 66 days to develop a new habit 21 days to create a new habit Huffington Post 21 days to create a new habit bad advice how long science has shown studies have thoroughly debunked the 21-day myth 66 days to create a habit it takes three months to form a new habit. Some say 66. experts 66 days