Each solstice or equinox I try to take a photo of the setting sun.   Tomorrow morning is the time of the Spring Equinox so I tried to get the moment when the sun sank below the horizon but unfortunately was a couple of minutes late and it was not as spectacular as yesterday.  In actual fact the equilux occurred a couple of days ago when the day and night were equal and days now are slightly longer than the nights.
The equilux is when day and night are equal and occurs a few days before the spring equinox, and a few days after the autumn equinox.
On the equinox, the length of day and night are only nearly equal. This is because the Sun appears as a disk in the sky, and the top half rises above the horizon before the centre. As well as this sunlight is refracted by the Earth's atmosphere. The Sun, therefore, appears to rise before its centre at the horizon, giving more daylight than you might expect (12 hours 10 minutes on the equinox).