What is the birth year of the Prophet, sallallaahu 'alayhi wa sallam, according to the Islamic and the Christian calendar?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Prophet Muhammad was born on Monday the ninth of the month of Rabi' al-Awwal from the Year of the Elephant (after the incident of Al-Feel), which is equivalent to April 20, 571 C.E.

Allaah Knows best.