How long has One Direction been a band?

They first auditioned for the X Factor in 2009 as solo artists. However, none of them got through as solo artists. But Simon Cowell called all 5 back and formed them into a group, which they settled for the name "One Direction".
In the X Factor live shows, they finished 3rd place, but were so popular by demand, Simon knew from the start that they would become a popular band.
That's how they formed. And now they're the best of friends!