And now, for the last two days, the rains on this lower course of the river had been incessant, so that the old men had shaken their heads and talked of sixty years ago, when the same sort of weather, happening about the equinox, brought on the great floods, which swept the bridge away, and reduced the town to great misery.
There are no more uses of "equinox" in the book.
Show samples from other sources
For a few minutes on the day of the equinox, the Sun’s radiation overwhelms the receiving station for the geostationary satellite.
According to Wikipedia, it is an urban legend that one can balance an egg on its point on an equinox day, but actually one can balance an egg on its point any day of the year with enough patience.