In late 19th Century, Nyingma Dzogchen Lama (central Tibet), Kushog Lungpo came to this valley and meditated at the holy sites of Raling. To celebrate the Lord Buddha's festival and enlightment at the time of Saga Debi Dui Chhen,Jeth Purni (Full Moon) festival was started. It takes place on full moon in May/June.
It is says, the oldest copper plate inscription of Ashoka Malla, the 12th century King of Sinja (Jumla) was also found here in Raling Gompa.
Lama established the Nyinbas (a Tibetan Community) and Tsangbas communities. So during the festival in gompa, Nyinbas and Tsangbas come dressed in their best. They wear their most valuable ornaments. On the born day of Lord Buddha, the non- celibate monks and nuns of all Nyinbas and other Tibetan speaking communities gather to do the ceremonies. They sing the songs of their beloved gods while circummambulating the monastery.
On personal note: Some of the information are taken from book Kailash Mandala (2nd edition) by Tshewang Lama.