What this calendar actually dates
The U.S. Naval Observatory defines primary phases by the Moon–Sun angular relationship. Full Moon occurs near an ecliptic-longitude difference of 180° and new Moon near 0°. In the Rashtriya Panchang, Purnima and Amavasya are the final tithis of the waxing and waning halves. They are intervals, rather than a single civil date. The table displays both the phase instant and each tithi’s calculated start and end.
For sunrise-based tithi labels, add your coordinates in the monthly tithi calendar. Read the phase and observance guide before treating a local phase date as a religious or regional calendar date.