In this article, I demonstrate that, of the two horoscopes transmitted by the Anonymous Commentary on Ptolemy’s ‘Tetrabiblos’, edited by Hieronymous Wolf, Basel, 1559, pp. 98 and 112, the first (H1 ) corresponds to an actual birth that took place in Lower Egypt on 25 June 448 AD, while the second (H2 ) is the same horoscope, slightly modified to fit the specific example for which it provides the illustration. The new date proposed here for H 1 is important for establishing a more precise chronology of the Anonymous Commentary, since it not only provides a terminus post quem for its composition (from the middle of the fifth century onwards) but also a particular geographical environment in the proximity of Alexandria. Given the large amount of formal and structural similarities which can be readily observed between the Anonymous Commentary and commentaries on Plato and Aristotle composed by Ammonius and his disciples in Alexandria, it becomes impossible not to link the work of the anonymous commentator to the Neoplatonic school of Alexandria of the fifth and sixth centuries, led by the philosopher Ammonius and his brother Heliodorus.
