Unduvap poya is the full moon day in the lunar month of Unduvap (in December). Unduvap commemorates the arrival of the Bo-tree sapling brought to Sri Lanka from India. It is the oldest documented tree in the world and is the tree that is venerated by Buddhists in Anuradhapura and around the world.  Also commemorates the establishment of the Bhikkhuni Sasana (the Order of Nuns).

There are twelve or thirteen poya days per year. Their names correspond to the Buddhist lunar months of the same name. They are VesākPosonEsalaNikiniBinaraVapIllUnduvapDuruthuNavamMedin and Bak.

If a month has two full moon days, the name of the second one is preceded by Adhi (meaning extra in Sinhala) as in Adhi Unduvap poya, etc.

Origin:

Pali, Sanskrit, Sinhalese