- The notation BCE ("Before Common Era") and CE ("Common Era") are alternative neutral notations for BC ("Before Christ") and AD ("anno Domini"), respectively.
- Zefram Cochrane builds warp drive on Earth and makes the first warp flight in Earth history in his experimental ship, the Phoenix. After his flight, first contact occurs between humans and Vulcans. (TOS: "Metamorphosis", Star Trek: First Contact)
- The title of Klingon Emperor is dissolved.
- The species known as the humpback whale becomes extinct at some point during this century on Earth. (Star Trek IV: The Voyage Home)
- Meanwhile, Earth's ozone layer deteriorates and the surface of the planet is flooded with ultraviolet radiation.
- A plant once considered to be a weed -- found in the rain forests of Earth's southern hemisphere -- is discovered to have medicinal properties, and to be a key element in the treatment of cancer. The plant is named Antony's Flower, after the scientist Lillian Antony. (TOS novel: Inception)
- A new age of medicine is heralded on Earth after Pyong Ko discovers the genetic sequence for inhibiting the growth of cancer cells. (VOY: "Fury")
|20th century|| Timeline|