Dwadashi

Dwadashi is the twelfth tithi of the bright fortnight, a Bhadra or wholesome tithi in the fivefold grouping. Its presiding deity is Vishnu, here in the aspect of Hari, and the day is closely tied to the Ekadashi fast that precedes it: the fast is traditionally broken on Dwadashi at the proper hour, a moment called parana, so the two tithis are observed as a devotional pair. Certain Dwadashis carry their own weight, such as the day associated with Vishnu's waking from cosmic sleep. The waxing Moon is now close to full. In the panchanga Dwadashi is read as auspicious and is bound up with Vaishnava observance. These are the conventions of the calendar and its devotional tradition.

Parana, the ritual breaking of the Ekadashi fast on the following Dwadashi, is governed by its own timing rules distinct from the ordinary tithi boundary: classical sources specify a window after sunrise and before a certain fraction of the Dwadashi has elapsed, and breaking the fast too early or too late is held to diminish its merit, so Dwadashi's devotional significance is defined as much by this precise sub-tithi timing as by the day's fivefold classification. The specific Dwadashi marking Vishnu's awakening, Prabodhini or Devutthana Ekadashi's paired Dwadashi in the bright fortnight of Kartik, closes the four-month period of Chaturmasya, during which several classes of auspicious activity, including weddings, are traditionally deferred until Vishnu is considered to have woken from his cosmic sleep.

The panchanga measures a tithi as an angle rather than a duration: one thirtieth of the circle the Moon travels away from the Sun and back again. Dwadashi occupies the arc from 132 to 144 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 Dwadashi carries Bava, first of the seven movable karanas, and the second Balava, the second movable karana. 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 waxing through this arc, setting later each evening and carrying about 87 per cent of the disc lit. That figure is a consequence of the definition rather than an observation added to it: elongation fixes the phase, so naming the tithi already names how much of the disc is lit.