The first day of the fortnight -- pratipada
The second day of the fortnight-- dvitiya
The third day of the fortnight -- tritiya
The fourth day of the fortnight -- chaturthi
The fifth day of the fortnight -- panchami
The sixth day of the fortnight -- shasti
The seventh day of the fortnight -- saptami
The eight day of the fortnight -- ashtami
The ninth day of the fortnight -- navami
The tenth day of the fortnight -- dashami
The eleventh day of the fortnight -- ekadashi
The twelveth day of the fortnight -- dvadashi
The thriteenth day of the fortnight -- trayodashi
The fourteenth day of the fortnight -- chaturdashi
The fifteenth day of the bright fortnight-- purnima
The fifteenth day of the dark fortnight-- amavasya
Each of the fifteen days may be especially sacred to a Deity so rituals related to specific Deities are timed in this way. The third is especially sacred to Lakshimi, the sixth to Subramanya, and the eleventh to Krishna or Vishnu. New moons or purnimas are considers very auspicious and a are considered an excellent time for meditation.