The Second Letter begins with Plato’s response to Dionysius’ complaint that Plato’s companions maligned him at Olympia. Bury notes: ‘Probably the Olympic Festival of 364 B. C. (not 360 B. C. as in Ep. VII. 350 B).’ Bury’s ‘probably’ is difficult to explain, for Plato returned from his final stay in Syracuse in 360 B. C. and in the Seventh Letter he refers to the Olympic games that he visited after his return to Athens:
‘On arriving at Olympia, in the Peloponnese (Elthôn de eis Peloponnêson eis Olumpian), I came upon Dion, who was attending the Games (Diôna katalabôn theôrounta); and I reported what had taken place (êngellon ta gegenêmena). And he (ho de), calling Zeus to witness (ton Dia epimarturamenos), was invoking me and my relatives and friends to prepare at once (euthus parêngellen emoi kai tois emois oikeiois kai philois paraskeuazesthai) to take vengeance on Dionysius (timôreisthai Dionusion) – we on account of his treachery to guests (hêmas men xenapateias charin), for that was what Dion said and meant (houtô gar elege te kai enoei), and he himself on account of his wrongful expulsion (auton d’ ekbolês adikou) and banishment (kai phugês). And I, when I heard this (akousas d’ egô), bade him summon my friends to his aid (tous men philous parakalein ekeleuon), should they be willing (ei boulointo) – “But as for me (Eme d’),” I said (eipon hoti), “it was you yourself, with the others (su meta tôn allôn), who by main force, so to say (bia̢ tina tropon), made me an associate of Dionysius at table and at hearth and a partaker in his holy rites (sussiton kai sunestion kai koinônon hierôn Dionusiô̢ epoiêsas); and he, though he probably believed (hos isôs hêgeito) that I, as many slanderers asserted, was conspiring with you against himself (diaballontôn pollôn epiboulein eme meta sou heautô̢) and his throne (kai tê̢ turannidi), yet refrained from killing me (kai homôs ouk apekteinen), and showed compunction (ê̢desthê de). Thus, not only am I no longer, as I may say, of an age to assist anyone in war (out’ oun hêlikian echô sumpolemein eti schedon oudeni), but I also have ties in common with you both (koinônos te humin eimi), in case you should ever come to crave at all for mutual friendship and wish to do one another good (an pote ti pros allêlous deêthentes philias agathon ti poiein boulêthête); but so long as you desire to do evil (kaka de heôs an epithumête), summon others (allous parakaleite).” (350b6-d4, tr. Bury)
Thus, we have every reason to believe that Plato wrote the Second Letter in 364 B.C., for we may presume that Dionysius complained to Plato about his being maligned at Olympia as soon as he heard about it, and his informers were eager to tell him about it as soon as they could.