There was a Golden Age to Islam once -- a Muslim Renaissance so magnificent, famous, cosmopolitan and cerebral that it's borders didn't always bleed. This era unequivocally produced some of the most enlightened thinkers throughout the Islamic Diaspora.
When Christians call for a Muslim Martin Luther, they are assuming not only that Islam lacks reformers but that Luther's version of Christianity is a perfect model that any Muslim reformer should strive to emulate.
The Islamic calendar does not begin with the year of Muhammad's birth, nor does it begin with the commencement of revelation to Muhammad. Rather, it begins with this purposeful move of the Prophet Muhammad from Mecca to Medina.