ART is not quackery (nor is chiropractic, but unfortunately that stigma has prevailed...). To become a certified ART practitioner, one has to spend a lotta time and money. In other words, the certification criteria appear to be pretty stringent. You may want to confirm your chiro is certified by the ART folks.
The Equinox (Vernal & Autumnal) There are only two times of the year when the Earth's axis is tilted neither toward nor away from the sun, resulting in a nearly equal amount of daylight and darkness at all latitudes. These events are referred to as Equinoxes.The word equinox is derived from two Latin words - aequus (equal) and nox (night). At the equator, the sun is directly overhead at noon on these two equinoxes.
The March equinox may be taken to mark the beginning of spring and the end of winter in the Northern Hemisphere but marks the beginning of autumn and the end of summer in the Southern Hemisphere. In astronomy, the March equinox is the zero point of sidereal time and, consequently, right ascension.