It is frequently the day of the Autumn Equinox in the Northern Hemisphere and the Vernal Equinox in the Southern Hemisphere. So says Wikipidia..
I say it is a time for warm hues and colors that make you feel the same way. The tone in your eyewear should follow the same mantra. Warm shades of brown, tortoise, lavender and plum. Choose you new fall season eyewear at atticeyewear.com