The dark fortnight
Sanskrit krishna (dark) + paksha (fortnight): the fifteen days from full moon to new moon.
The half of the lunar month in which the moon wanes. Dhanteras and Naraka Chaturdashi fall in the dark fortnight of Kartika, and Diwali on its new moon.
Ekadashi is the sacred eleventh lunar day of Vishnu, kept with fasting, prayer and restraint of the senses. Its origin, fasting levels and Parana explained.
The Panchang, Hinduism's lunar-solar calendar, tracks the relationship between Sun and Moon across five limbs to determine auspicious timings and festivals.
Full moon and new moon mark the two climactic points of the lunar cycle, one turned toward radiant celebration and the other toward stillness and ancestors.
From the Brahmavaivarta Purana, truthful King Harishchandra regains his kingdom, wife, and resurrected son by observing Aja Ekadashi.
The sacred story from the Brahmavaivarta Purana of King Indrasena delivering his departed father from Yamaloka to Vaikuntha on Indira Ekadashi during Pitru Paksha in Ashvina Krishna Paksha.
The katha from the Brahma Vaivarta Purana in which Krishna tells Yudhishthira how worshipping Vishnu with Tulsi on Kamika Ekadashi cleanses an accidental sin.