But Night and Day Aren't The Same Length!
Spring has arrived. Confused as to why day and night aren't equal on this day? Here are some reasons why:
A look in your almanac will reveal that day and night are not exactly 12 hours long at the equinox, for two reasons:
First, sunrise and sunset are defined as when the Sun's top edge - not its center - crosses the horizon. Second, Earth's atmosphere distorts the Sun's apparent position slightly when the Sun is very low.

Have these facts on hand when you get the inevitable calls at the equinox from people saying your sunrise and sunset times must be wrong because they are not 12 hours apart.