Mahalaya Paksha Shraddh (Pitru Paksha Shraddh) are the rituals dedicated to Pithru devatas or dead ancestors. In 2013, Mahalaya paksha or Pitru Paksha 2013 shraddh starts on September 20 and ends on October 4 with Mahalaya Amavasya Tarpan.
Mahalaya Pitru paksha begins on the first day during Ashwin month as per North Indian calendar followed in Uttar Pradesh, Madhya Pradesh, Bihar, Himachal Pradesh, Jharkhand, Chhattisgarh, Uttarakhand, Delhi and Rajasthan.
But, as per the calendars followed in Gujarat, Maharashtra, Andhra Pradesh and Karnataka, Mahalaya Pitru Paksha Shraddh begins on the first day in second half of Bhadrapad maas. Though, as per Gregorian calendar Mahalaya Shraddh Paksha begins on the same day in both Panchangs (In 2013, on September 20).
As per North Indian calendars, Mahalaya Shraddh paksha ends on Mahalaya Amavasya or Ashwin Amavasya which falls on October 4 in 2013. As per the other calendars mentioned above, Mahalaya Pitru Shraddha Paksha ends on Mahalaya Amavasya or Bhadrapad Amavasya which also falls on October 4.
On the next day to Mahalaya Amavasya, Sharad Maha Navaratri or Durga Maha Navratri begins.
Read the detailed list of Pitru Paksha 2013 dates (Mahalaya Paksha 2013 schedule).