According to the principles of special relativity, time dilation occurs when an object moves relative to an observer at speeds approaching the speed of light, not when it slows down to zero velocity.
When an object approaches the speed of light, time dilation occurs, meaning that time appears to pass more slowly for the moving object compared to a stationary observer. This effect is symmetric, meaning that both observers, the one moving at high speed and the stationary observer, perceive time differently from each other.
However, when an object slows down and eventually comes to rest (zero velocity) relative to another observer moving at or near the speed of light, the time dilation effect is no longer present. In this case, time will pass at the same rate for both the stationary observer and the object that has come to rest.
It's important to note that the effects of time dilation and length contraction are specifically associated with objects moving at relativistic speeds, close to or approaching the speed of light. At low velocities relative to the speed of light, the effects of time dilation and length contraction are negligible and not noticeable in everyday situations.