Pseudo-Dionysius the Areopagite (or Dionysius the Pseudo-Areopagite) was a Greek[1] author, Christian theologian and Neoplatonic philosopher of the late 5th to early 6th century, who wrote a set of works known as the Corpus Areopagiticum or Corpus Dionysiacum.
Dionysius' identity is still disputed. Corrigan and Harrington find pseudo-Dionysius to be most probably...
... a pupil of Proclus, perhaps of Syrian origin, who knew enough of Platonism and the Christian tradition to transform them both. Since Proclus died in 485, and since the first clear citation of Dionysius' works is by Severus of Antioch between 518 and 528, then we can place Dionysius' authorship between 485 and 518-28.