An equinox is an astronomical event in which the plane of Earth’s equator passes through the center of the Sun which occurs twice each year, around 20 March and 23 September. 

The March equinox is known as the Vernal Equinox, or, in the northern hemisphere, as the Spring equinox.  The September equinox is known as the Autumnal equinox, or, in the northern hemisphere, as the Fall equinox.

A Solstice is an astronomical event that occurs twice each year (around June 21 and December 21) as the Sun reaches its most northerly or southerly excursion relative to the celestial equator on the celestial sphere.

NB. In a country like Australia with a variety of timezones it is inevitable that, at times, these Equinox and Solstice rides fall on different days in different timezones. Please double check the IBA page for GMT link and calculate from there.