The Importance of Il November Poya Day:

By Premasara Epasinghe, The Daily News, Sri Lanka, November 12 2008:

The Il Poya falls on November fullmoon. It is the last Poya of the "vassa" Rainy Season retreat
and a number of important incidents occurred on this day.
Therefore, it is a significant day in the Buddhist calendar:

First of all it celebrates the Future Buddha: Metteyya Bodhisatta but also other events:
1: The announcement of the future Buddhahood of Metteyya Bodhisatta,
2: The first Buddhist Missionary activity by sending out the Sixty Arahats,
3: The Jatila Brothers entering the Buddhist Sangha,
4: Festival of "Devaharohana" or Ascend to heaven by Gotama Buddha,
5: Acceptance of a Robe from the future Buddha Metteyya, who was a disciple of the Buddha.
6: Passing away of the Chief Disciple Sariputta of Gotama Buddha.
7: The relic Dakunu Aku Datuwa right canine tooth, put in the first Dagoba Thuparama Chaitya.

Further, Buddhist in Sri Lanka Commemorate Il Poya as the "Cheevara Masaya." The
offering of "Katina Cheevaraya" is considered as a highly meritorious act, which take
place in most of the Temples during the month of Il. The Katina Cheevara is brought to
their respective temples in processions and offered to the resident Upasampada
monks, who observed Vas. (Rainy Retreat) for nearly three months.

1: The Future Buddha Metteyya:
Metteyya Bodhisatta was born to a high caste family in the City of Sankassa, during the
time of Gautama Buddha. His father's name was Siriwaddha. Metteyya had a complete
Education under the Great Teacher Disapamok. After entering the Order, and at the
end of the Rainy Season, Metteyya Thera, received a very valuable pair of robes. He
donated one of the robes to Gotama Buddha.

After receiving the robe the Blessed One uttered thus:-
"Dear Monks, this Bhikkhu will be the future Buddha. He will be born in a kingdom known
as Ketumati. The Emperor of this Kingdom will bear the name Sankha. His father's name
will be Brahma and he will be the Chief Consultant to the king. His mother's name will be
Brahmavati. He will attain Buddhahood under a Naga tree.

2: Sakyamuni Buddha addressed the first sixty Arahats thus:
Oh! Bhikkhus for the Welfare of the many, for the Happiness of the many, through
Compassion to the World, Go Ye Forth, and spread the Doctrine of Buddha Dhamma for
the benefit of Devas and Human Beings) In this manner, the first Buddhist Missionaries
commenced their journey on Il Poya day to various directions.

3: The Jatila Brothers
The three Jatila Brothers Uruwela, Nadi, Gaya, lived in Hermitages close to the River
Neranjana. They had thousand disciples. The Blessed One, proceeded to the hermitage
of Jatila Uruvela and performed "Pelahara" spiritual powers or super natural magic and
later converted all three brothers and their followers to Buddhism.

6: Passing Away of Sariputta Thera
The passing away of Sariputta, Senior Chief Disciple, occurred on Il Poya day. A week
before he passed away, he visited his beloved mother Rupasari, who did not believe in
the Triple Gem. She was residing in a village named Nalaka, in the Magadha Province.
Sariputta Thera's main ambition was to make his mother a follower of Buddhism. After
listening to her son Sariputta's sermon, she attained Sotapanna or the first stage out
of four stages towards the realization of liberation.

Video on Uposatha Observance:
https://www.youtube.com/watch?v=cUIDQd19OmY

Audio on Uposatha Observance Praxis ..
https://soundcloud.com/bhikkhu-samahita/observance-praxis-uposatha

The Buddhist Poya Uposatha Observance Day Calendar is here:
https://What-Buddha-Said.net/various/Poya.Uposatha.Observance_days.htm