Yes, according to the theory of relativity, time dilation occurs not only when objects are moving at high speeds but also when there is a difference in relative motion between observers. This means that time dilation can occur both when an object is moving quickly relative to another object and when it is slowing down relative to another object.
When an object slows down, it experiences time dilation compared to a reference frame that remains in motion at a constant velocity. This effect is known as "time dilation due to relative velocity" and is a consequence of the principle that the speed of light is constant in all inertial reference frames.
In the case of an object slowing down, its relative velocity decreases, and as a result, time appears to pass faster for that object compared to the reference frame that remains at a constant velocity. This means that clocks on the slowing-down object would run faster relative to clocks in the reference frame.
It's important to note that the magnitude of the time dilation effect is dependent on the velocity or acceleration of an object relative to the reference frame. As an object approaches the speed of light, the time dilation effect becomes more pronounced. Conversely, as an object slows down, the time dilation effect diminishes until it becomes negligible at low speeds.
So, while time dilation is often associated with objects moving at high speeds, it also occurs when objects slow down relative to other frames of reference.