An Indian emperor carved five Greek kings' names into rock — anchoring his own dates
Around 256 BCE the emperor Ashoka had edicts inscribed across his realm naming five contemporary Hellenistic kings to whose lands he had sent missions of dhamma — among them Ptolemy II Philadelphus of Egypt and Antiochus II of the Seleucid realm. Because the reigns of those Greek rulers are independently known, the stone edicts give historians a rare fixed anchor for dating Ashoka's own reign.
How we know
Ashoka's Major Rock Edict XIII names Antiochus II Theos, Ptolemy II Philadelphus, Antigonus II Gonatas, Magas of Cyrene, and Alexander (of Epirus or Corinth), inscribed c.257–256 BCE. The overlapping, independently-dated reigns anchor Ashoka's own dates. The Library of Alexandria was begun under Ptolemy I and built out under Ptolemy II.
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