March equinox equinox. This is most notable at the more extreme latitudes, where the Sun may be seen to travel sideways considerably during the dawn and evening, drawing out the transition from day to night. At the north and south poles, the Sun appears to move steadily around the horizon, and just above the horizon, neither rising nor setting apart from a slight change in declination of about 0.39° per day as the equinox passes. The Babylonian calendar began with the first full moon after the vernal equinox, the day after the Sumerian goddess Inanna's return from the underworld (later known as
Equinox Equinox An equinox is commonly regarded as the instant of time when the plane (extended indefinitely in all directions) of Earth's equator passes through the center of the Sun. This occurs twice each year: around 21 March and 22–23 September. In other words, it is the moment at which the center of the visible Sun is directly above the Equator. In the northern hemisphere, the equinox in March is called the Vernal or Spring Equinox; the September equinox is called the Autumnal or Fall Equinox. However, because the Moon (and to a lesser extent the other planets) cause the motion