Two times each year, when night and day become equals, equinox dragons reveal themselves. Celebrations for the arrival of these dragons vary greatly, but villages graced with their presence are said to have an especially bountiful harvest. Wizards have since proven this tale to be untrue, but the festivals are so fun, they keep that little secret.
The Equinox Dragon's description states, "when night and day become equals, equinox dragons reveal themselves." This is likely a reference to the fact that during the equinox, night and day are of equal length.