When was Israel divided?

According to the Bible, the United Monarchy called Israel was divinded into the separate kingdoms of Judah and Israel shortly after the beginning of the reign of Rehoboam, or perhaps a little earlier than 900 BCE.

Archaeologists such as Israel Finkelstein say that there never was a united monarchy, and that Israel and Judah had always been separate, with their own identifiable cultures, pottery and even separate dialects of the Hebrew language. Therefore, Israel never was divided.