Ephemeris Time is a time scale used in astronomy to provide a consistent measure of time based on the positions of celestial bodies. It was developed in the mid-20th century to improve the accuracy of astronomical calculations, particularly for predicting the positions of planets and other objects in the solar system. Unlike standard timekeeping systems, Ephemeris Time is based on the motion of the Earth and other celestial bodies, making it more precise for scientific purposes. It has since been largely replaced by Barycentric Dynamical Time (BDT) but remains important in the history of timekeeping in astronomy.