In the movie *Interstellar*, is the time dilation the team suffers on the water planet Miller caused by the proximity of the planet to Gargantua or by the planet's gravitational pull?

In the beginning I thought it was caused by the black hole, but later I was reading [this article][1] and the guys said it was caused by the planet. Do we have some information about this?

  [1]: http://www.theguardian.com/film/filmblog/2014/nov/05/interstellar-astrophysics-does-space-science-work-out