Krishna Dashami

Krishna Dashami is the twenty-fifth tithi overall, the tenth day of the dark fortnight, sharing the character of the tenth tithi, whose presiding deity is traditionally Yama, lord of dharma. It is a Purna or full tithi in the fivefold grouping and so read as relatively stable. The waning Moon is now a slim crescent in the pre-dawn sky, drawing close to the Sun. The panchanga reads the tenth tithi of either fortnight as generally favourable, though the dark fortnight's diminishing light tempers its use for auspicious beginnings. These are the conventions of the Hindu luni-solar calendar, which counts thirty tithis to the month and gives each a character partly from its number and partly from its paksha.

Yama's connection to the tenth tithi, carried into the waning fortnight without the countervailing triumph of Vijayadashami that colours the bright-fortnight Dashami so strongly, leaves the dark Dashami read more straightforwardly through Yama's role as upholder of dharma and order rather than through any specific festival narrative, since no major all-India observance is fixed to this particular waning tenth day. As a Purna tithi it retains its generally stable character within the dark fortnight even so, one of several waning-fortnight tithis where the fivefold classification's inherent favourability partially offsets the general caution the tradition applies to the diminishing half of the month.

The tithi is the oldest of the five limbs of the panchanga and the least intuitive, because it is defined by an angle in the sky and not by a sunrise. Krishna Dashami occupies the arc from 288 to 300 degrees of that separation. Because the Moon travels an elliptical orbit its angular speed is not constant, so that twelve degree arc is crossed in anywhere from roughly nineteen to roughly twenty six hours. The convention that resolves this is simple and consequential: the civil day takes the name of the tithi that is running at sunrise. 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 Dashami carries Vanija, the merchant's karana, and the second Vishti, the karana also called Bhadra. Vishti is the one karana the muhurta literature marks as unfit for beginnings, and its presence in the second half is why this tithi is read with more care than its neighbours. 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 30 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.