Krishna Tritiya

Krishna Tritiya is the eighteenth tithi overall, the third day of the dark fortnight. It shares the character of the third tithi, a Jaya day associated with victory and with the goddess Gauri, but the Moon is now clearly waning. The panchanga treats the third tithi of either fortnight as generally favourable. In some regions particular dark-fortnight tithis carry festivals of their own, and the ongoing diminution of the Moon shapes which observances are chosen. These are the calendar tradition's conventions; the astronomical basis is simply the Moon closing the twelve-degree steps back toward conjunction with the Sun, each tithi marking one such step regardless of whether the light is growing or fading.

Gauri's identification with Tritiya persists across the waning fortnight exactly as it does in the bright half, and several regional fasting observances dedicated to her, kept by married women for the wellbeing of their husbands and households, are specifically timed to the dark-fortnight Tritiya in certain months rather than to the more widely known bright-fortnight Akshaya Tritiya, showing that the two Tritiyas of a month are not simply a bright, festive version and a quiet, unremarkable counterpart but each carry their own distinct devotional life in different regional traditions. As with every tithi in the waning half, its real clock-time duration is governed by the same Moon-Sun angular arithmetic as the bright fortnight, unaffected by which half of the month it falls in.

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 Tritiya occupies the arc from 204 to 216 degrees of that separation. Since lunar motion quickens and slackens across the month, the arc is crossed in as little as about nineteen hours or as much as about twenty six. The panchanga settles the mismatch by naming each civil day for the tithi in force at its 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 Tritiya 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 93 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.