Time dilation was one of the vocabularywords listed on the chart "A Tunnel in the Sky".
This chart was seen in the schoolroom aboard Deep Space 9 in 2369. (DS9: "In the Hands of the Prophets")
The core of Dilmer III created a spacetime differential, resulting in time dilation. For every second on the USS Cerritos, a week passed on the planet's surface. (LD: "Fully Dilated")
