In Hinduism, each lunar phase has religious and astrological significance. There are four principal (primary, or major) lunar phases: the new moon, first quarter, full moon, and last quarter (also known as third or final quarter), when the Moon's ecliptic longitude is at an angle to the Sun (as viewed from the center of the Earth) of 0ð, 90ð, 180ð, and 270ð respectively. Hindu astrology also considers significant the changes in the phase of the moon even during the course of each individual day.
The first of these principal phases is AmÃÂvásyà(), the day of the new moon.
The second and fourth phases (the quarters) are less significant, marking only the midpoints of the Paksha (), the fourteen days on either side of the full moon. There are two pakshas: the first is the 'brightening' (Shukla) of the moon, as it changes from new to full; the second is the 'darkening' (Krishna), as it changes from full to new.
The first day of a paksha is called a Pratipada () or Prathama () and thus there are two of these days (the first and usually the fifteenth of the lunar month).
The third phase is Pà «rá¹Âimà(), the day of the full moon.
In the pà «rá¹ÂimÃÂnta mÃÂna Hindu lunisolar calendar used in most parts of the Indian subcontinent, the lunar month starts on the day following the full moon and therefore AmÃÂvásyàalways falls in the middle of the month. However, in the amÃÂnta mÃÂna calendar used in some places, the lunar month starts on the day of the new moon, making AmÃÂvásyàthe last day of the lunar month in those places. Many festivals, the most famous being Diwali (), are observed on AmÃÂvásyÃÂ.
In Vedic timekeeping, a tithi is a "duration of two faces of moon that is observed from earth". Every day of a lunar month is called tithi. This concept is significant in astrology as it maps to the moment of birth.
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