(covers information from several alternate timelines)
A temporal matrix was an integral component of 29th century Federation timeships. The temporal matrix had to be precisely recalibrated when creating a temporal rift, otherwise the resultant unstable temporal field could lead to a massive temporal explosion.
Such an explosion occurred in an alternate timeline in the 29th century, when Henry Starling, an industrialist from the 20th century, piloted the Federation Timeship Aeon into the future, causing the destruction of all of Earth's solar system. This timeline was later negated when the USS Voyager, which had been transported back in time from 2373 to 1996, managed to destroy the Aeon with a photon torpedo moments before it entered the rift, thereby changing history in that the explosion never occured. (VOY: "Future's End", "Future's End, Part II")