Vesak (the full moon Poya day in May)
The Buddhist calendar begins with the month of Vesak. On Vesak Day, Buddhists world over commemorate the triple anniversary of Sakyamuni Siddhartha Gautama, the Buddha. It is a triple anniversary in honor of the birth of the Buddha, his attainment of Supreme Enlightenment at the age of thirty five, and after a successful ministry of forty five years attained Parinirvana or passed away on a Vesak (May) full moon Poya Day. It was also on a Vesak full moon Poya Day, in the eighth year of his enlightenment, that the Buddha made his third and final visit to Sri Lanka.

Poson (the full moon Poya day in June)
This day commemorates the introduction of Buddhism to Sri Lanka by Arahat Maha Mahinda (son of King Asoka of India) at Mihintale in the third century BCE. The Venerable Mahinda established the Dispensation of the Buddha (Buddhasasana) in Sri Lanka.

Esala (the full moon Poya day in July)
Commemorating the deliverance of the first sermon to the five ascetics and setting in motion the Wheel of the Dhamma (Dhammachakka) at Sarnath Benares, India. The essence of the first sermon is the explanation of the Four Noble Truths: The Noble Truth of Suffering or dissatisfaction or conflicts (Dukkha), the cause of suffering, the cessation of suffering and the path leading to the cessation of suffering and the the Noble Eight-fold Path.

Nikini (the full moon Poya day in August)
During the month of August the conducting of the first Dhamma Sangayana (Convocation) is commemorated. This was held three months after the passing away of The Buddha. Five hundred Arahat Theros participated in the convocation which was held over seven months in the cave at the foot of the Rajagahanuvara Vebhara Rock.

Binara (the full moon Poya day in September)
Commemorates The Buddha's visit to heaven to preach to his mother and celestial multitude. It also commemorates the commencing of the Bhikkhuni (nun's) Order. Pajapati Gotami approached The Buddha and implored him to establish the Bhikkhuni Order.

Vap (the full moon Poya day in October)
The significant events commemorated during this month are: the conclusion of The Buddha's preaching of the Abhidhamma for three months to his mother in the Heavenly realm (devaloka), and King Devanampiyatissa of Sri Lanka sending envoys to King Asoka requesting him to send his daughter Arahat Sanghamitta Theri to Sri Lanka to establish the Bhikkhuni Sasana (Order of Nuns).

Ill (the full moon Poya day in November)
This day celebrates the obtaining of Vivarana (the assurance of becoming a Buddha) by the Bodhisatta Maitriya and the commissioning of 60 disciples by the Buddha to disperse his teachings. It also marks the conclusion of the three month retreat (vassana).

Unduvap (the full moon Poya day in December)
A celebration to honor the arrival of the sacred Bo-tree sapling. This was brought to Sri Lanka from India by Buddhist Theri Sanghamitta, and it is this very tree that is venerated by Buddhists in Anuradhapura. It is also the oldest documented tree in the world. Sanghamitta Theri established the Bhikkhuni Sasana (the Order of Buddhist Nuns).

Duruthu (the full moon Poya day in January)
In honour of Lord Buddha's first visit to Sri Lanka. This visit also took place in the first year of the Buddha's Supreme Enlightenment.

Navam (the full moon Poya day in February)
Celebrating the following events in Buddhist history: The entrance into the order of two leading disciples of The Buddha (Sariputta and Maha Moggalana), the Buddha proclaiming for the first time, a code of fundamental ethical precepts for the monks. The Buddha announcing that within three months His Parinibbana (death) will take place.

Medin (the full moon Poya day in March)
This day commemorates the visit of the Buddha to his home to preach to his father King Suddhodana and other relatives and show them the path to enlightenment and final deliverance.