Ashtami, the Day of the Half Moon

Ashtami is the eighth tithi of the bright fortnight, falling close to the first-quarter Moon when the disc is about half lit. In the fivefold grouping it is a Jaya tithi, associated with victory. Its presiding deity is traditionally Rudra, a fierce form of Shiva, and the goddess Durga is strongly linked to the eighth tithi as well. Durga Ashtami, in the bright fortnight of Ashvin, is one of the most important days of the Navaratri festival. In some reckonings Krishna is held to have been born on the eighth tithi of the waning fortnight, the festival of Janmashtami. The panchanga treats Ashtami with some caution for ordinary undertakings while honouring its many festivals. These are the calendar tradition's associations, anchored to the half-Moon of the waxing quarter.

Durga Ashtami's position within Navaratri places it at the traditional close of the nine nights' worship of the Goddess in her nine forms, immediately before Navami, and in several regional traditions the two tithis are observed together as Ashtami-Navami, blurring into a single extended culmination rather than being treated as two fully separate days. Krishna's traditional birth on the waning-side eighth tithi, at midnight in the month of Bhadrapada, is calculated by most panchangas according to the tithi prevailing at midnight itself rather than at sunrise, which occasionally produces disagreement between regional almanacs about which calendar date Janmashtami should be observed on, since the tithi in force can differ between the two reference moments in a given year.