which event marks the start of the islamic calendar
Islamic calendar The Islamic calendar employs the Hijri era whose epoch was retrospectively established as the Islamic New Year of AD 622. During that year, Muhammad and his followers migrated from Mecca to Yathrib (now Medina) and established the first Muslim community (ummah), an event commemorated as the Hijra. In the West, dates in this era are usually denoted AH (Latin: Anno Hegirae, "in the year of the Hijra") in parallel with the Christian (AD) and Jewish eras (AM). In Muslim countries, it is also sometimes denoted as H[1] from its Arabic form ( سَنة هِجْريّة, abbreviated هـ). In English, years prior to the Hijra are reckoned as BH ("Before the Hijra").[2]
Treaty of Hudaybiyyah The Treaty of Hudaybiyyah (Arabic: صلح الحديبية) was an important event that took place during the formation of Islam. It was a pivotal treaty between Muhammad, representing the state of Medina, and the Quraysh tribe of Mecca in March 628 (corresponding to Dhu al-Qi'dah, 6 AH). It helped to decrease tension between the two cities, affirmed a 10-year peace, and authorized Muhammad's followers to return the following year in a peaceful pilgrimage, later known as The First Pilgrimage.[1][2][3]