Guru Brahma Guru Vishnu. Guru Devo Maheswara .Guru Sakshath Para Brahma .Thasmai Shri Gurave Namaha.Guru Poornima is celebrated to honor our teachers and mentors. In our Hindu culture Guru(Teacher) has got a great value. Hindus show much respect to their gurus. Gurus are often regarded as God. The day, also known as “Vyasa Purnima” is observed by devotees who offer pujas (worship) to their beloved Gurus. Sage Vyasa is known to be the Adi (original) Guru of the Hindu religion. The auspicious day of Vyaasa Poornima has a great significance as everybody knows that the role of a Guru in real life is very much important.
The day also finds a great importance for farmers. The period 'Chaturmas' ("four months") begins from this day. The water, drawn up and stored as clouds in the hot summer, now manifests in plentiful showers that brings fresh life everywhere.
Poornima & Moon - Poornima is the Full-moon day and is known for its spiritual importance and significance. Poornima dates are calculated according to the moon's position. As we all know that the moon passes through many stages till it reaches the Full-moon day. It takes fifteen days to reach the Full-moon day and fifteen days for the no moon day. No moon day is known as Amawasya in Hindu calendar. As the moon circles the Earth, the shape of the moon appears to change; this is because different amounts of the illuminated part of the moon are facing us. The shape varies from a full moon (when the Earth is between the sun and the moon) to a new moon (when the moon is between the sun and the Earth).
Astrologically, Guru is represented by Jupiter, the only planet that has the potency to nullify any affliction caused by the other planets. It represents the higher mind, the vision of truth, and the principles of growth, expansion, and optimism.