Well, "linked" is vague. They aren't linked—they are the same thing! Gravity is an effect mass has on the upholstery of the universe. Time runs slower for us here inside the gravity well of Earth than it does for astronauts in zero gravity.
You can't create time distortions without gravity distortions, and you can't create gravity distortions without instantiating mass, so... big massive black holes have to be running slow; if they exist at all and aren't just cosmic bees sitting at the 2D boundary of the universe and projecting nothingness into our inflated space.
If you're speaking of time and space, no, they're different -- they're certainly all part of one spacetime, but they're distinct. This distinct:
t' = t √(1-v^2/c^2)
t = time
v = velocity
c = speed of light
t' = time at velocity v relative to velocity 0
Put into words, this special relativity relationship shows that an increase in velocity (movement in space) causes a reduction in time's rate of passing (movement in time). The general relativity version has more terms, and shows a relationship between mass and both space and time.
So space, time and mass aren't the same thing, but they're part of an interrelated system, one easily described mathematically.
> Time runs slower for us here inside the gravity well of Earth than it does for astronauts in zero gravity.
Yes, true, but astronauts in orbit aren't in zero gravity, they're in free-fall. The gravitational force at typical orbital heights is nearly as strong as it is at the surface.
You can't create time distortions without gravity distortions, and you can't create gravity distortions without instantiating mass, so... big massive black holes have to be running slow; if they exist at all and aren't just cosmic bees sitting at the 2D boundary of the universe and projecting nothingness into our inflated space.