Answer
299 BC marks the beginning of Pharnavaz's reign, as proposed by Cyril Toumanoff. This date is based on the assumption that Pharnavaz ascended to the throne shortly after the death of Alexander the Great in 323 BC and ruled for approximately 65 years. Toumanoff's chronology aligns with archaeological evidence and historical accounts, providing a plausible framework for understanding the early history of the Kingdom of Iberia.