Tarpana differs from the more elaborate shraddha rites in frequency and setting rather than in the powers it addresses: for initiated men who maintain the traditional daily observances, tarpana is folded into sandhyavandanam, the twilight prayers recited at fixed points of the day, making the offering of water to ancestors, sages, and gods a routine, near daily component of ordinary religious life rather than a rite reserved for special occasions, in clear contrast to shraddha's more periodic and occasion bound character.
Alongside this daily thread, the Hindu calendar sets aside a specific annual period, Pitru Paksha, the fortnight of the ancestors, falling in the lunar month before the autumn festival season, during which tarpana and related ancestral offerings are considered especially important and are observed by many households that do not perform the rite daily the rest of the year, treating the fortnight as a concentrated annual occasion for an obligation that in principle could be discharged at any time. This combination of a routine daily obligation for the initiated few and a widely observed annual season for households generally reflects how thoroughly ancestral offering is woven into the calendar at more than one register, a continuous quiet thread running underneath an annual period of heightened, more widely shared attention to the same underlying duty.