Complex sentence: Year 337 BC was a year of the pre-Julian Roman calendar.In the Roman Empire it was known as the Year of the Consulship of Longus and Paetus (or, less frequently, year 417 "Ab urbe condita").
Split into simpler sentences: Year 337 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Longus and Paetus (or, less frequently, year 417 "Ab urbe condita").