Complex sentence: Year 351 BC was a year of the pre-Julian Roman calendar.In the Roman Empire it was known as the Year of the Consulship of Peticus and Crispinus (or, less frequently, year 403 "Ab urbe condita").
Split into simpler sentences: Year 351 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Peticus and Crispinus (or, less frequently, year 403 "Ab urbe condita").