Making a door swing open/close smoothly?

Since this has been asked before, I'll just copy and paste my answer from another question.

Here's how you rotate a part around a point (or in your case, a door).

part.CFrame = origin*rotation*(origin:inverse()*part.CFrame)

origin is the point (CFrame, not Vector3) you're rotating around, and rotation is the CFrame you're rotating by.

You can use a simple for loop to make it open smoothly.

local origin = CFrame.new(Door.Position - Vector3.new(Door.Size.X/2,0,0))
for i = 1, 18 do
	Door.CFrame = origin * CFrame.Angles(0,math.rad(90/18),0) * (origin:inverse()*Door.CFrame)
	wait()
end