Final answer:
The creation of the Islamic community at Medina in 622 CE, known as the hijra, is the event that marks the starting point of the Islamic calendar.
Step-by-step explanation:
The starting point of the Islamic calendar is marked by the hijra, or emigration, of the prophet Muhammad and his followers from Mecca to Medina in the year 622 CE. This significant event not only represents the creation of the Islamic community at Medina but also signifies the transition of Islam from a small, persecuted religion to a societal force with a united community. The hijra demonstrates the survival and establishment of Islam as a significant world religion and symbolizes the beginning of a new era, which is reflected in the Islamic lunar calendar commencing from that year, labeled as AH, which stands for 'After the Hijra'.