When you reach the singularity of a black hole, time stops for you since you have been obliterated. Time does not halt for you just because you pass through the event horizon of a black hole. Instead, you will experience infinite gravitational time dilation as you are stretched out over an infinitely large area while remaining motionless. This means that you will never age and die in a black hole, but instead you will be crushed into nothing by the force of gravity over an eternity of time. The reason we know time stops in a singularity is because no signal can escape from it. If time stopped for everyone, then there would be no way to tell if a star went supernova or not, or if a galaxy collapsed into a black hole or not. Since we can't make such observations, time must stop for those inside the singularity. In fact, according to general relativity, nothing can escape the pull of a black hole except information. That's why many scientists believe that black holes may actually be portals to other dimensions where information is transmitted between worlds. However, this isn't the only reason time might stop inside a black hole. There could be any number of reasons why this might happen, including but not limited to: quantum mechanics, string theory, etc.