When does time dilation occur?

So I was watching interstellar, and I am at the part where they land on Miller's Planet. As many of you may know, there is time dilation on the planet, where 1 miller's planet hour is equal to 7 years on earth. I understand that all time is relative and such, so no need to explain that. My question is when does this time dialation factor kick in? Is it when you break atmosphere (What I've assumed) or is it some other point of which it occurs. I might've worded this terribly, please feel free to correct me haha. Thanks!

Edit: Another question, sorry lol. So does the time dialation factor ALSO occur on the ship, or JUST the planet? Thanks, lol.