Temporal reflection
A temporal reflection, also known as a time-delayed reflection, is a phenomenon which can be produced by the spatial irregularities found in a quantum singularity. Due to the chaotic nature of the spacetime distortions, this can cause events to be observed after or even before they actually took place.

An analogy of this type of reflection was described by B'Elanna Torres as "You're sitting at the bottom of a pond, which is frozen over and you look up at the surface and you see a reflection of yourself. Now you might think you're looking at another person sitting at the bottom of another pond looking back at you."

In 2371, the  encountered a distress call in the Delta Quadrant, and discovered a vessel trapped within the event horizon of a type-4 quantum singularity. 

It was soon discovered, however, that the vessel they detected was actually Voyager itself, and the distress signal was actually their opening hail to the vessel, reflected back through time by the singularity's event horizon. 

Realizing that they were the ones trapped within the event horizon, Captain Kathryn Janeway and  B'Elanna Torres piloted a shuttlecraft to widen a breach in the horizon with a dekyon beam, so Voyager could escape. 

While returning to Voyager, they encountered a temporal reflection of the ship, making it appear as if there were two Voyagers. Deducing that the ship that was stationary was the real one, due to the fact that they were holding position in anticipation of the shuttle's return, Janeway and Torres were able to dock with Voyager, and the ship was able to escape. ()

time travel