While in France he wrote his world-renowned paper Sur la Stabilité du Système Solaire (On the Stability of the Solar System) and also published over one thousand astronomical observations.

He returned to Greece and revived the Athens Observatory breaking it into three divisions Astronomy, Meteorology, and Geodynamics.

Eginitis received countless honors and awards throughout his life including the French medal Legion of Honour.

He studied mathematics with some of Greece's most brilliant minds of the time namely John Hazzidakis, Cyparissos Stephanos, Vassilios Lakon, and Nikolaos Nikolaidis.

For two years Demetrios traveled around France and England working at different astronomical facilities namely the meteorological centre of Parc Saint Maur, the Meudon Observatory, the Observatory of Nice and Lockyer’s astronomical laboratory in England.

While he was at the Paris Observatory Eginitis also studied the secular variations of the semi-major axes of planetary orbits under the supervision of Ernest Mouchez.

The work was entitled Sur la Stabilité du Système Solaire (On the Stability of the Solar System).

Greek astronomer Demetrios Kokkidis managed the Observatory with no salary for a short period making minor advancements in the field of astronomy.

By the year 1895, Eginitis established three departments within the National Observatory of Athens: Astronomy, Meteorology, and Geodynamics.

By 1896, he became professor of Meteorology and Astronomy at the University of Athens a position he held until 1934, roughly thirty-eight years.

[14][15] A vast European network of railroads connected with Greece and a universal timezone was necessary to communicate with the rest of the world.

Eginitis persuaded the Greek Government to adopt the Eastern European Time Zone on July 28, 1916.

Eginitis lobbied the church and state to follow the uniform internationally accepted calendar.

The oration was given by the Dean of the School of Physics and Mathematics of the University of Athens Chemistry professor Konstantinos D. Zeghelis.

Laplace concluded that any two planets and the Sun must be in mutual equilibrium and thereby launched his work on the stability of the Solar System.

Eignities built on this research and performed similar calculations for Earth, Jupiter, and Saturn using complex mathematics.

Eignities concluded the Earth would approach the Sun for 20,000 years and then the semi-major axis of orbit will start to increase for a specific period and the cycle will continue.

Eginitis postulated that the variations in the average distance to the Sun were so minuscule that it would not have an effect on Earth.

Because of his work, he gained the respect of the international astronomical community, and Camille Flammarion specifically congratulated his efforts.