Avani avittam - The day to atone for one's sins - Hindu Brahmins

Traditionally, Brahmins were charged with the study, teaching, and chanting of the Vedas as their main vocation.
Brahmacharis were boys who had undergone their spiritual (second birth) with the yajnopaveetam and initiation into the Gaayatri mantra.
They would typically spend eight years learning a particular Veda from their guru in a school called paatasala.
Upakarma literally means acts/work (karma) to be done before (upa).
It comprises the preparatory acts done before starting Vedic studies every year. For students of the Yajur Veda, Upakarma falls on the full moon day in the month of Aavani, hence it is also called Aavani Avittam. For Rig Vedis, it is the day prior to the full moon day, and for Sama Vedis it is on the day of Ganesh Chaturthi.

The rituals done on Upakarma day are for starting the next year's Vedic studies on an auspicious note by atoning for various shortcomings or wrongdoings, seeking blessings from the rishis and gods, and by charging up the Brahmachari's spiritual batteries for fruitful learning in his new semester.

Kamokaarsheet Manyurakaarsheet Japam: Kaama (desire) and manyu (anger) are the root causes of all our sorrows. This japam is chanted 108 times to submit all our misdeeds deriving from these demons to be burnt up by the deities of kaama and manyu.

Brahma Yajnam: The first few mantras of each of the four Vedas are chanted to symbolically mark the beginning of the new Vedic school year.

Maha Sankalpam: This is a long invocation that identifies the participants in terms of their lineage and spatial and temporal coordinates in the Hindu cosmos, specifies the syllabus of studies they wish to undertake, purifies them ritually, and expresses their resolve (sankalpam) to learn and teach the Vedas properly.

Yajnopaveeta Dhaaranam: The sacred thread, yajnopaveetam, symbolizes our oneness with Brahman, the ultimate reality. The three strands in the original yajnopaveetam which is vested during Upanayanam (the Gaayatri mantra initiation ceremony) represent various triads that are very important in Hinduism � Brahma, Vishu, and Shiva; the letters A, U, and M of the most potent Vedic sound OM; the ida, pingala, and sushumna nadis through which the Kundalini shakti has to be properly channeled for spiritual advancement; the three gunas sattva, rajas, and tamas; etc. It is also a visible symbol of the authority and competence of the person wearing it for carrying out his Vedic duties. A new yajnopaveetam is worn (dhaaranam), with mantras asking for it to impart spiritual effulgence (Brahma tejas). The old thread is then removed and discarded.

Kaandarishi Tharpanam: The Vedas were seen in the meditative trances of our ancestral rishis (seers), who codified them into various sections, called kaandas. Obeisance with water offering (tharpanam) is given to them in this ritual, asking for their blessings before commencing new learning.

Sravana Homam: Agni, the Vedic deity of fire, is the divine carrier of our oblations and invocations to all the gods. During this homam (fire ceremony), the students ask to be blessed for their learning to proceed without obstacles and then chant and hear (sravana) sample sections from the four Vedas, and also from auxiliary scriptures called Vedangas, as a token of commencing their studies. The teacher declares that their studies have formally begun. The students offer their dakshina to the teacher and partake of the prasaadam before disbursing.

Gaayatri Japam: This is done the morning of the day following the Upakarma ceremony. Traditionally, all Brahmins are supposed to chant the Gaayatri mantra 108 times during the three sandhyas (the Sun's transition periods; dawn, noon, and twilight) each day. The Gaayatri mantra is the most powerful and sacred of all Vedic mantras. Its meaning is: Om is verily this world, the mid-region, and heaven (the three spheres of the cosmos); We meditate on the divine effulgence of that adorable Sun (Savitar) of spiritual consciousness; May He stimulate our power of spiritual insight. As a mantra, it has great potency if it is chanted properly, even if its meaning is not understood, though meditating silently with complete awareness of its meaning has greater benefits. The Gaayatri mantra is the quintessence of the Vedas and it has the power to bestow protection, health, longevity, prosperity, creativity, spiritual radiance, and ultimately moksha (liberation via self)realization of our oneness with Brahman. It is chanted 1,008 times on the day following Upakarma to make up for not chanting it regularly during the previous year.