The astrophysicist Vasilios N. Manimanis , PhD of the University of Athens, forewords.

The present work, which is being published for the first time in modern Greece, is a thorough study of the movements of the Sun which result in the lengths of the Earth's days and nights according to its various positions on the Ecliptic in relation to the points of the tropic .

This work of the great mathematician and astronomer Theodosius consists of two books (chapters). The first book contains 12 sentences and the second 19.

In between, Theodosius quotes various auxiliary propositions, conclusions and lemmas, and mentions propositions from other astronomical works. Specifically from Euclid's "Phenomena" and "On a Moving Sphere" by Autolycus of Pitaneos. He even refers to propositions from his wonderful work "Spherics", which is a thorough theoretical mathematical study of the sphere.