I tend to think of the equinoxes and solstices as happening on the 21st of the months in which they occur. There's a simple reason for this: my birthday is March 21, and when I was growing up I was told that my birthday was the first day of spring. (Of course this is only true in the northern hemisphere. To anyone reading this in the global South, my apologies for the boreocentrism.) I loved the idea that spring began on my birthday, and it fascinated me to think on the equinoxes, everywhere in the world gets 12 hours of daylight. (There's a lovely image of this at Wikipedia if you'd like a visual aid.)
I've since learned that technically the equinoxes and solstices don't always fall on the 21st of their requisite months. (This year, for instance, the September Equinox falls today, on September 22.) Also that it's not exactly true that everywhere in the world gets exactly 12h of light on the equinoxes. That equinox page tells me that "during the time of the September and March equinoxes many regions around the equator have a daylight length of about 12 hours and six-and-a-half minutes. Moreover, the day is slightly longer in places that are further away from the equator and the sun takes longer to rise and set in these locations."
But even if it isn't scientifically exact to think that the equinoxes are cosmic balance-points, when the earth is perfectly poised between one season and the next, on a spiritual level this idea still really works for me -- especially coming, as this one does, during the Days of Awe. I like to think that today our planet pauses, perfectly aligned, before beginning to tilt again.
The equinoxes (and solstices) are times of year when I'm especially conscious of changing light. Today the earth's tilt is vertical, neither toward the sun nor away from it; tomorrow we begin to shift. In my hemisphere, this is the official first day of autumn. Though in south Texas where I grew up that didn't really mean much, in New England where I've lived for the past seventeen years the outside world is already visibly changing. High places in my region had their first frost a couple of nights ago. (We didn't, here at our house, but it was a near thing; it's coming soon.) The angle of light at my desk has changed. While most trees here are still green, here and there a branch or a whole tree is alight with red or gold, the first flames of fall.
This shift puts me in mind of other shifts which are on their way. By the time we reach the first day of winter -- even if he is late in coming, as many first babies are -- my son will have emerged from my body and entered the world. This is the last season before his birth.
[T]he ancient book of Jubilees tells that on the night of the autumn equinox, Abraham looked up to the stars to try to see the future. At that moment, the Holy One spoke to him. As the nights grow longer, we spend time telling the stories of our ancestors and remembering our traditions. From this, we learn who we might become.
That's from Yom Kippur and the Autumn Equinox: A Comparison by Rabbi Jill Hammer, published at Tel Shemesh in a year when the two days were right up next to one another. It was from Reb Jill that I first learned the traditional Jewish blessing recited on the equinox (which can be found in Talmud:) ברוך אתה ה' אלהינו מלך העולם עושה בראשית / Baruch atah Adonai, eloheinu melech ha'olam, oseh vereishit. (Blessed are You, Adonai our God, Source of all being, who makes creation.)
The precise moment of equinox today has been calculated to fall at 21:19 UTC, which will be 5:19pm here in my time zone. I haven't decided yet whether I'm going to go outdoors and make this blessing at that moment, or whether I will find a time which arises organically out of my day when I can go outdoors, breathe deeply of the autumnal air, and bless the Source Who fills and fulfills all things. Either way, today is a hinge-point between what has been and what is coming. What, in your life, is poised on the cusp of change?