On this equinox the decrease in sunlight per day is at its greatest rate. Then the amount of sunlight lost per day rate decreases until the Winter Solstice, at which time it reaches zero and then we get increases in sunlight per day.
In the Spring Equinox, the rate of increase per day is at its greatest rate.
If you plot amount of sunlight per day vs. days, the resulting curve is a shift of a cosine function.
Now, that you know all that, carry on with your day!