Ali ibn al-Athir
The date of the attack on Sinope and the ensuing siege of Trebizond can be determined from three sources: John Lazaropoulos, Michael Panaretos, and Ali ibn al-Athir. John Lazaropoulos dates these events to the Byzantine year of the world 6371, in the second year of the reign of Andronikos I Gidos; the Byzantine year started on the first day of September and ended on the last day of August, and because Alexios I died 1 February 1222, it is clear the second year of the reign of Andronikos began in February 1223, Lazaropoulos' dating points to some time between February 1223 and September of the same year. The "Chronicle" of Michael Panaretos uses exactly the same words to date the defeat of Melik, so we can be assured the siege also fell within this time period. But Lazaropoulos does not usually provide us with exact dates: this is the only one in his writings. Beyond providing the sequence of actions, he provides no information how much time passed between the rapacious acts of Etoumes, the Trapezuntine raid on Sinope, and the beginning of the siege itself, making it possible the first two happened earlier—perhaps years—before 1223. Fortunately our third source, Ali ibn al-Athir, mentions that in 1223 a ship of refugees from the Mongols sank off Anatolia which was then plundered by the Seljuks; so it is clear all three events happened over this six-month period between February and September 1223.