Paksha

A lunar month in the Hindu calendar has two fortnights, with each fortnight subdivided into lunar days called tithis. A paksha consists of 15 such tithis, each of which correspond to a 12-degree angular motion of the Moon. The fortnight between amavasya and purnima is called as Shukla Paksha (bright side) or Gaura Paksha, which corresponds to the period of the waxing moon. The second fortnight is called Krishna Paksha (dark side) or Vadhya Paksha' and corresponds to the period of the waning moon. Amavasya corresponds to the period when the Moon is within 12 degrees of angular distance from the Sun before their conjunction.

A lunar month begins on the next day after amavasya in the amanta tradition and on the next day after purnima in the purnimanta system. The amanta system is followed majorly in the South India and the purnimanta system in North India.

Shukla Paksha

Shukla Paksha refers to the bright lunar fortnight in the Hindu calendar, corresponding to the waxing moon. Shukla is the Sanskrit word for "white" or "bright". The Shukla Paksha is a period of 15 days, which begins after the amavasya (new moon day) and culminating on purnima (full moon day) and is considered auspicious.

Numerous festivals are held during this period, including the Navaratri festivals, most importantly Chaitra Navaratri and Ashvin Navaratri.