Should Mahalaya Paksha Shrardh be performed only on the Tithi of Parents? What are the alternate tithis on which one can perform Mahalaya Paksha Shrardh?

Pt. Shri. Khape Vasudevachar

Shrardh

Previous (Should all brothers join together and perform Mahalaya Paksha Shrardh jointly or can it be done separately in different locations on same or different tithis?)     |     Next (What is Pitrusesha? What is the Significance of it?)