Lunar phase

The four main phases

Hindu astrology and religious practice give the moon's phases a place of their own. Four of them are counted as principal: the new moon, the first quarter, the full moon and the last quarter, which is also called the third or final quarter. What separates them is the angle between the Moon and the Sun, measured from the Earth's centre, at nought, ninety, one hundred and eighty and two hundred and seventy degrees. Smaller shifts matter too. The tradition also notes how the moon's appearance changes within a single day, not only from one day to the next.

Bright and dark halves

Each lunar month here is built from two pakshas, or fortnights, of fourteen days each, sitting on either side of the full moon. The first is Shukla, the half in which the moon brightens. The second is Krishna, the half in which it darkens. The two quarter phases have a smaller part to play: they mark the midpoint of each fortnight and little more. The opening day of a paksha is called Pratipada, or sometimes Prathama. Since a month holds two fortnights, that first day comes round twice, usually as the first and the fifteenth day of the lunar month.

Two ways of counting months

Places that follow the pūrṇimānta māna calendar begin a lunar month on the day after the full moon. Under that reckoning, which is used across most of the Indian subcontinent, the new moon always lands somewhere in the middle of the month. Other places use the amānta māna calendar, which starts the month on the new moon day itself. There, Amāvásyā closes the lunar month instead of splitting it. So the same moon, seen on the same night, can be the middle of one calendar and the end of another.

The tithi day

Vedic timekeeping gives the lunar month its own set of days, the tithis. A tithi is described as the span of two faces of the moon, watched from the earth. Each tithi is one day of the lunar month. Hindu astrology treats it as significant, because it maps to the moment of birth. Two of these days carry their own names as well: Amāvásyā, the new moon day, and Pūrṇimā, the full moon day.

Festivals on the new moon

Amāvásyā is more than a marker in the sky. Many Hindu festivals are observed on the new moon day. The best known is Diwali, whose name means the festival of lights. Pūrṇimā, the full moon day, is also named in the tradition. Because regions count their months differently, a festival tied to a lunar day can fall at a different point in the sequence depending on where it is kept. For the people who follow these dates, the moon works as a calendar: its dark night is a day like any other, with its own name and place.

How Lunar phase is kept

Hindus who follow the lunar calendar watch the moon through the month. The new moon day, Amāvásyā, and the full moon day, Pūrṇimā, are named and observed. The first and last quarters are noted mainly because they sit at the middle of the two fortnights. The lunar month is divided into tithis, and astrologers read the tithi of a person's birth. Families and priests consult these dates when fixing festivals, and Diwali, the best known of them, is kept on Amāvásyā.

When and where

The dates follow the moon, so they drift against the solar year. A lunar month is made of two fortnights of fourteen days, one on either side of the full moon. Whether Amāvásyā sits in the middle of the month or at its end depends on the counting system a region keeps.

This belongs to India and the wider Indian subcontinent, where the lunisolar calendar sets the dates of festivals. The pūrṇimānta māna system, which opens the month after the full moon, is used across most of the Indian subcontinent. Some places instead keep the amānta māna system, opening the month at the new moon.

What Lunar phase means

Inside the practice, the moon's two halves are read as light growing and light fading, and the new moon is a turning point in the month while the full moon is its high point. Vedic astrology also ties the tithi of a birth to the person born then, so the phase at that moment is taken as meaningful rather than incidental.

Days Lunar phase is marked

Questions people ask about Lunar phase

See also

NowruzThe Iranian new year at the March equinox, kept with fire, greenery and picnicsIndian national calendarIndia's official civil solar calendar, designed to bring unity to timekeepingPongalThree or four days of boiling rice, garlanded cattle and thanks to the sunLosarThe Tibetan Buddhist New Year festival of renewal, offerings, and family feasts

Good reading and sources

• Lunar phase (Hinduism) on WikipediaEncyclopedia
• Wikidata recordOpen data

It may contain mistakes. Traditions differ from one family, village and community to the next, and the people who keep them know them best. If something is wrong, tell us. Last refreshed 2026-10-12.