Arrival of the Bo-tree (Dumindagamanaya) and establishment of the Bikkhuni Order in Sri Lanka was a great significant event on Unduvap Full Moon Day. 

Theri Sanghamitta and her eleven nuns arrived in Sri Lanka with the Jaya Sri Maha Bodhi. The King Devanampiyatissa welcomed them. This event occurred around the year 240 B.C. This Sacred Bo-tree is venerated by Buddhists globally. It is also the oldest documented tree in the world.

Therini Sanghamitta established Bhikkhuni Sasana by ordaining many ladies as Bhikkunis. The First Sri Lankan fully ordained Bhikkunis were Princes Anula, sister-in law of the King, Utthara, Aggimitta, Peggu, Pabbatha, Malla, Dharmadayi, Hema and Masaraga