Amavasya is the term used in the Hindu lunar calendar to denote the new moon day, which marks the end of Krishna Paksha (the waning phase of the moon) and the beginning of the next lunar cycle. It is a significant day in Hindu culture and spirituality, characterized by the absence of visible moonlight.

Amavasya is the time during which the Moon stays dark when viewed from Earth. It is a scientific phenomenon happening due to the Moon getting in between the Sun and the Earth.  However, according to ancient history, it happens because Chandra Dev was cursed by his father-law to slowly fade out of existence and then saved by Lord Shiv, making this vanishing phase eventually lead to Chandra gaining back his full form. Thus began the cycle of New Moon to Full Moon to New Moon again. It is the time of the new Moon when the Moon temporarily ceases to exist when viewed from Earth, while Poornima is the time when it is a Full Moon. Amavasya is generally considered to be the most inauspicious time of the month. However, it is also considered as virtuous as the Poornima.

Key Features of Amavasya:

1. Timing:
   • Day of the New Moon: Amavasya occurs when the moon is in conjunction with the sun, and its illuminated side faces away from Earth, making it invisible in the night sky. It typically happens once a month, although the exact date can vary depending on the lunar calendar and regional traditions.
2. Cultural and Religious Significance:
   • Ancestral Worship: Amavasya is particularly significant for performing rituals and offerings to honor ancestors (Pitru Paksha). This is a time when many Hindus perform Shraddha (ancestral rites) to seek blessings for the well-being of departed souls and to offer gratitude and respect.
   • Spiritual Cleansing: The new moon day is considered a powerful time for spiritual practices, including meditation, fasting, and cleansing rituals. It is believed that the absence of moonlight enhances the effectiveness of spiritual activities aimed at inner purification and renewal.
3. Festivals and Observances:
   • Diwali: Amavasya in the month of Kartik is celebrated as Diwali, the Festival of Lights. This major Hindu festival marks the return of Lord Ram to Ayodhya after defeating Ravan. People light lamps and firecrackers to symbolize the victory of light over darkness and good over evil.
   • Mahalaya: The Amavasya of the month of Ashwin is known as Mahalaya, which marks the end of Pitru Paksha. It is an auspicious day for performing rites for ancestors and is considered a key day for honoring the souls of the departed.
4. Astrological Importance:
   • Muhurta: In Vedic astrology, Amavasya is sometimes chosen for performing certain rituals, such as initiating new ventures or making important decisions, depending on the planetary alignments and the specific requirements of the activity.
5. Moral and Ethical Symbolism:
   • Reflection and Renewal: Amavasya symbolizes a time of reflection, letting go of the past, and preparing for new beginnings. It is a day to focus on personal growth, spiritual development, and the clearing of negative energies.

Popular Stories and Legends Associated with Amavasya:

1. The Story of Karn:
   • Legend: In the Mahabharat, the story of Karna highlights the significance of Amavasya. Karna, after his death, ascended to heaven but found himself being served gold and jewels instead of food. He realized that he had never offered food to his ancestors during his lifetime. He was granted the opportunity to return to Earth for 15 days to perform Shraddha rituals for his ancestors, which is why Amavasya became an important day for honoring one’s forebears.
2. The Legend of Dhanvantari:
   • Story: On the Amavasya of the month of Kartik, it is believed that the divine physician Dhanvantari emerged from the ocean during the churning of the ocean (Samudra Manthan) carrying the nectar of immortality. This day is sometimes associated with health and healing rituals.
3. The Legend of Lord Vishnu and the Churning of the Ocean:
   • Story: The churning of the ocean, which produced various divine treasures including the poison that Lord Shiv consumed, is linked with Amavasya. This act is symbolic of the cosmic cycle of creation, preservation, and destruction, often observed during the new moon phase.

In summary, Amavasya is a day of spiritual significance, associated with ancestral worship, personal reflection, and renewal. It is a time for engaging in purification rituals, honoring ancestors, and preparing for new beginnings. The day holds cultural and religious importance and is marked by various festivals, observances, and legends that highlight its spiritual significance.