Which tirthankara do historians date to the eighth or seventh century BCE?

1. The 23rd tirthankara, Parshvanatha, was likely a historical being. 2. Jain tradition dates him to the ninth century BCE, while historians say the eighth or seventh century BCE. 3. Mahavira is dated later, to the sixth or fifth century BCE. _Source: Wikipedia, Jainism, Origins: Parshvanatha and Mahavira_