Krishna Pratipada

Krishna Pratipada is the sixteenth tithi overall and the first of the Krishna or dark fortnight, the waning half of the lunar month that begins just after the full moon. It shares the character of the first tithi, a Nanda day in the fivefold grouping, with Agni or Brahma as presiding deity, but now the Moon's light is beginning to diminish rather than grow. In some regional reckonings, particularly in northern India, the month is counted from the day after the full moon, making this the start of the month itself. The panchanga reads the early waning days as suitable for certain kinds of consolidation while the waxing days are preferred for fresh beginnings. These are the conventions of the calendar tradition, resting on the Moon's slow return toward the Sun after opposition.

The convention, followed in some regional calendars, of beginning the lunar month on the day after the full moon rather than after the new moon is called the purnimanta system, as against the more widespread amanta system that starts the month at the new moon; the two produce the same sequence of tithis but disagree about which month a given stretch of days belongs to, so a date can carry two different month-names depending on which regional convention is followed even though the tithi itself is identical in both. This is a genuine source of confusion when comparing almanacs from different parts of India, and neither system is more classically authoritative than the other, both being attested in different regions and different classical astronomical texts.

A tithi is not a day. It is an arc, the interval in which the Moon gains twelve degrees of longitude on the Sun, and the civil day merely borrows its name. Krishna Pratipada occupies the arc from 180 to 192 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 Pratipada 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 now past opposition and waning, rising later each night and lingering into the morning sky. Through this tithi the disc shows over ninety-nine per cent of the disc lit, a disc the eye reads as full. This is also the point at which the purnimanta and amanta reckonings part company: the same tithi opens a new month in the north and continues the old one in the south.