True Solar Time
Time based on the actual position of the local sun, with noon occurring at the moment the sun is at its highest point. It can differ from clock time by several tens of minutes.
True Solar Time is calculated based on the actual observed position of the sun at a given location, with noon defined as the moment the sun reaches its highest point. Because the Earth's orbit is elliptical and its axis is tilted, the length of a true solar day varies, leading to differences ranging from a few to several tens of minutes compared to modern standard clock time. In traditional Chinese metaphysics, when calculating a person's Ba Zi (Eight Characters), their birth time must be converted to True Solar Time to more accurately correspond to the celestial conditions at that moment.