The full moon day in the Hindu month of Ashad (July-August) is observed as the auspicious day of Guru Purnima, a day sacred to the memory of the great sage Vyasa. All Hindus are indebted to this ancient saint who edited the four Vedas, wrote the 18 Puranas, the Mahabharata and the Srimad Bhagavata. Vyasa even taught Dattatreya, who is regarded as the Guru of Gurus.
On this day, all spiritual aspirants and devotees worship Vyasa in honor of his divine personage and all disciples perform a 'puja' of their respective spiritual preceptor or 'Gurudevs'.
This day is of deep significance to the farmers, for it heralds the setting in of the much-needed rains, as the advent of cool showers usher in fresh life in the fields. It is a good time to begin your spiritual lessons. Traditionally, spiritual seekers commence to intensify their spiritual 'sadhana' from this day.
The period 'Chaturmas' ("four months") begins from this day. In the past, wandering spiritual masters and their disciples used to settle down at a place to study and discourse on the Brahma Sutras composed by Vyasa, and engage themselves in Vedantic discussions.