When did Sufism start?

Shaykh Fadhlalla Haeri (The Thoughtful Guide to Islam) regards the development of Sufism as natural and progressive, rather than being founded at a particular time or place. Hasan al-Basri was regarded as one of the early Sufis, without necessarily having been named as such during his life. By the early eighth century, an increasing number of people had chosen a way of life based on ascetism, meditative and other ritualistic practices, such as chanting the name of God as a means of enhancing remembrance of Allah and maintaining self-awareness. By the ninth century, a large body of teachings from the traditions and Sunnah emphasised the importance of gaining knowledge of the self in order for higher and more subtle knowledge to become accessible. By the twelfth century, tasawwuf, or knowledge of self, was a recognised part of religious life and came to be taught in many madrasahs and many Sufi Orders became established.