According to Dio himself, he had been collecting material for his work for 10 years and working over the main part of his «Roman History» for 12 years. The author of the paper shows that the terminus post quem for the beginning of the first stage is 201, while the second one could not come to an end later than 229. Precise chronology does not seem to be determinable, but one can infer that Dio began to collect his material under Septimius Severus and that the bulk of writing was made in the 220s. There might have been a pause between the two periods. Book LXXX (and perhaps some other final books) was written after 229, after Dio had moved back to his native Bithynia.