The basic experiment involves either a sand or water clock. The period of one noon to the next full cycle would generate different volumes of water and sand reflecting the variation in the total length of each individual cycle . If the volumes were combined and divided equally by the number of cycles, an average would be created . This is how the average 24 hour day is created regardless of method or complications.

The Equation of time is the bridge between the unequal quantities (natural noon) and equal quantities (24 hour noon). The bridge which correlates the 24 hour weekday to the natural day is anchored to noon and is a global observation along any line of longitude so it doesn't involve any seasonal components, for example, when it is noon at Conception in Chile, it is also noon in New York as they share roughly the same longitude line but different seasons however both locations will register the same length of the noon cycle as per water/sand clock.