Guru Purnima (Poornima) also known as Vyasa Purnima marks the birthday of Ved Vyasa.[3] It is a spiritual tradition in Hindu culture dedicated to spiritual and academic Gurus, who are evolved or enlightened humans, ready to share their wisdom with very little or no monetary expectation, based on Karma Yoga. It is celebrated as a festival in India, Nepal and Bhutan by the Hindus, Jains and Buddhists. This festival is traditionally observed by Hindus, Buddhists and Jains to revere their chosen spiritual teachers / leaders and express their gratitude. The festival is celebrated on the full moon day (Purnima) in the Hindu month of Ashadha (June–July) as it is known in the Hindu calendar of India.[4][5]

The celebration of Guru Poornima is marked by spiritual activities and may include a ritualistic event in honor of the Guru; that is, the teachers which is called Guru Pooja. The Guru Principle is said to be a thousand times more active on the day of Guru Purnima than on any other day.[7] The word Guru is derived from two words, gu and ru. The Sanskrit root gu means darkness or ignorance, and ru denotes the remover of that darkness[8]. Therefore, a Guru is one who removes the darkness of our ignorance.[3] Gurus are believed by many to be the most necessary part of life. On this day, disciples offer pooja (worship) or pay respect to their Guru (spiritual guide). In addition to having religious importance, this festival has great importance for Indian academics and scholars. Indian academics celebrate this day by thanking their teachers as well as remembering past teachers and scholars.
Many Hindus celebrate the day in honor of the great sage Vyasa, who is seen as one of the greatest Gurus in ancient Hindu traditions and a symbol of the Guru-shishya tradition. Vyasa was not only believed to have been born on this day, but also to have started writing the Brahma Sutras on ashadha sudha padyami, which ends on this day. Their recitations are a dedication to him, and are organised on this day, which is also known as Vyasa Purnima.[11][12][13] The festival is common to all spiritual traditions in Hinduism, where it is an expression of gratitude toward the teacher by his/her disciple.[14] Hindu ascetics and wandering monks (sanyasis), observe this day by offering puja to their Guru, during the Chaturmas, a four-month period during the rainy season, when they choose seclusion and stay at one chosen place; some also give discourses to the local public.[15] Students of Indian classical music and Indian classical dance, which also follow the Guru shishya parampara, and celebrate this holy festival around the world. According to the Puranas, Lord Shiva is considered the first Guru.
Legend

This was the day when Krishna-Dwaipayana Vyasa – author of the Mahabharata – was born to sage Parashara and a fisherman's daughter Satyavati; thus this day is also celebrated as Vyasa Purnima.[12] Veda Vyasa did yeoman service to the cause of Vedic studies by gathering all the Vedic hymns extant during his times, dividing them into four parts based on their use in the rites, characteristics and teaching them to his four chief disciples – Paila, Vaisampayana, Jaimini and Sumantu. It was this dividing and editing that earned him the honorific "Vyasa" (vyas = to edit, to divide). "He divided the Holy Veda into four, namely Rig, Yajur, Sama and Atharva. The histories and the Puranas are said to be the fifth Veda."