Krishna Pratipada, the First Waning Day

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.