How is it possible for black holes to decay?

I have read that black holes decay over time. But I have also read that because of the enormous gravitational force near black holes that time basically comes to a stop on the surface of a black hole. If time stops in or on a black hole, I don't understand how it could decay.|||The decay doesn't happen at or below the event horizon. The virtual particle pairs erupt from the vacuum at some small height above the horizon where time still ticks away. If one falls into the black hole before the pair can collapse back to the vacuum, the hole must change its mass by a negative amount to balance the one remaining.