Tachyonic matter (also known as tachyons) is a type of matter that always moves FTL. However, they move STL, due to the infinite amount of negative energy necessary to do this. They have imaginary mass, so they are not subject to tritemporal dilation. They always move backward in time.
The confirmation of tachyons' existence happened in 2594 CE by a Simudian researcher, using an atemporal calibration of the sensors. However, he was not able to stabilize them, because of their time direction.
Hypertachyons are tachyons that move forwards in time, but backward in the imaginary time. They were discovered in 12508 CE and stabilized in 14295 CE. In 14337 CE, the first hypertachyon transmitters were invented, replacing the outdated QMEU method of FTL communication.
Recent researches to stabilize tachyons are being made, and maybe it will allow the creation of tachyonic antitelephones. However, some futurists say that it will only be possible by 230000 CE.