Equinox and Equilux
Thanks to this post at TimeAndDate.com, I learned today about the Equilux*!
Despite common belief, day and night are not equal on the Equinox. The Equinox is when the sun crosses the the celestial equator, so it rises due east and sets due west.
Day and night are equal lengths on the Equilux, which is either a few days before or after the Equinox.
The post above also has a link to help you find the Equilux in your location.
And now you have two days to celebrate!
*Not to be confused with Equilux Horse Cleaner Spray.