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.