Dwitiya

Dwitiya is the second tithi, the second lunar day of the waxing Shukla fortnight. Like every tithi it measures a twelve-degree gain of the Moon over the Sun rather than a fixed span of clock time, so its length varies from day to day. It belongs to the Bhadra group of the fivefold tithi classification, the wholesome or auspicious days, and its presiding deity is traditionally Brahma the creator. As an early day of the waxing Moon it is regarded in the panchanga as suitable for founding and building, the light of the Moon still growing. The Chandra Darshan, the ritual first sighting of the young crescent, is observed on this tithi in many regions. These are traditional almanac associations; the underlying reality is the slender crescent visible soon after new moon.

Because a tithi is timed from one sunrise to the next for civil purposes, Dwitiya, like every tithi, can occasionally fall victim to kshaya, vanishing from the calendar in a given month if its full twelve-degree span happens to elapse between two sunrises, or to vriddhi, being repeated across two days if its span happens to straddle two sunrises. The Chandra Darshan observed on this tithi is timed independently by the actual visibility of the crescent at dusk rather than by the arithmetical tithi boundary alone, since a very thin crescent can be lost in twilight glare even when the tithi has technically begun, which is why almanac makers give a separate visibility calculation for the observance alongside the tithi reckoning proper.

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. Dwitiya occupies the arc from 12 to 24 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 Dwitiya 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 waxing through this arc, setting later each evening and carrying about 2 per cent of the disc lit, a thread visible only in twilight. 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.