Krishna Ashtami

Krishna Ashtami is the twenty-third tithi overall, the eighth day of the dark fortnight, falling near the last-quarter Moon when the disc is again about half lit. It shares the character of the eighth tithi, associated with Rudra and with the Goddess, and it is a Jaya tithi. In the Vaishnava tradition Krishna is widely held to have been born on this waning-side eighth tithi in the month of Bhadrapada, the festival of Krishna Janmashtami, one of the most important of the year. In some Shaiva reckonings the dark eighth tithi, Kalashtami, is kept for Bhairava. The panchanga treats Ashtami with some caution for ordinary matters while honouring its major festivals. These belong to the calendar and devotional tradition.

Kalashtami's dedication to Bhairava, Shiva's fierce form, situates it within a distinct current of Tantric and Shaiva practice separate from the Vaishnava weight the eighth tithi carries through Janmashtami in the bright fortnight, and the two festivals, one to a fierce guardian deity and one to a gentle, playful incarnation of Vishnu, sit on opposite sides of the same month without direct connection beyond sharing the number eight. Krishna Janmashtami's calculation, like several major festival tithis, depends on which tithi prevails at a specified hour, in this case midnight, rather than at sunrise, and disagreement between regional panchangas about the correct reference moment is a recurring, publicly debated feature of the festival's annual dating.

Reckoning a tithi means measuring elongation, the angular distance of the Moon from the Sun, and cutting that circle into thirty equal twelve degree arcs. Krishna Ashtami occupies the arc from 264 to 276 degrees of that separation. The Moon does not move at a fixed rate, and the same twelve degrees may take a little over nineteen hours near perigee or close to twenty six near apogee. A calendar has to name whole days, so the rule is that whichever tithi is current at sunrise gives the day its name. A tithi shorter than the interval between two sunrises can therefore be skipped entirely, which the tradition calls a kshaya tithi, and one longer than that interval can carry its name over two civil days, an adhika or vriddhi tithi. Both occur in the ordinary course of a year, and both are why an observance can appear on two dates in the same almanac.

Each tithi is halved again, and each half carries a karana, so the first half of Krishna Ashtami carries Balava, the second movable karana, and the second Kaulava, the third. Seven of the eleven karanas repeat, cycling eight times through the month, while four are fixed to particular half tithis at the month's opening and close.

The Moon is waning through this arc, rising later each night and showing about 50 per cent of the disc lit. The phase follows from the elongation and not the other way round, so the tithi and the shape of the disc are two readings of one measurement.