Hellenistic astrology encompasses the techniques developed in the ancient Mediterranean world between the third century BCE and the seventh century CE. The primary texts, from authors like Vettius Valens, Dorotheus of Sidon, and Claudius Ptolemy, describe a system that is both more structured and more nuanced than modern popular astrology.
The foundational difference from modern Western astrology is the use of whole sign houses, sect, essential dignities, and time-lord systems. Planets are not simply in signs — they have varying strength depending on whether the chart is a day or night chart, whether the planet is in a sign it rules or a sign where it has dignity, and what planetary period the native is currently running.
Annual profections move the chart forward one house per year of life, activating a sign, a house topic, and a time-lord planet that colors all transits for that year. Zodiacal Releasing, drawn from Valens, uses the Lots to produce a major/minor period structure spanning decades. Together, these techniques give Hellenistic astrology its reputation for precise timing.
Astrolium implements all of these tools using the Swiss Ephemeris, with full support for day/night sect switching, Ptolemaic essential dignity tables, and the complete set of seven Hermetic lots.