Autumn Equinox 2025 Uk Time. Usually, when we talk about the first day of autumn we are referring to the astronomical autumn which is defined by the earth's axis and orbit around the sun. The meteorological and astronomical methods.
Find out more about equinoxes and solstices. On the day of the winter (december) solstice, the sun passes through the southernmost point of the ecliptic, that is, as far as possible from the celestial equator to the south (for the northern.