The Uposatha (Sanskrit: Upavasatha) is a Buddhist day of observance, in existence from the Buddha’s time (500 BCE), and still being kept today in Buddhist countries. The Buddha taught that the Uposatha day is for “the cleansing of the defiled mind,” resulting in inner calm and joy. On this day, both lay and ordained members of the sangha intensify their practice, deepen their knowledge and express communal commitment through millennia-old acts of lay-monastic reciprocity. On these days, the lay followers make a conscious effort to keep the Five Precepts or (as the tradition suggests) the Eight Precepts. It is a day for practicing the Buddha’s teachings and meditation.

Observance days

Depending on the culture and time period, uposatha days have been observed from two to six days each lunar month.

Theravada countries

In general, Uposatha is observed about once a week in Theravadin countries in accordance with the four lunar phases: the new moon, the full moon, and the two quarter moons in between. In some communities, such as in Sri Lanka, only the new moon and full moon are observed as uposatha days.

In Burma, Uposatha (called ဥပုသ်နေ့ ubot nei) is observed by more pious Buddhists on the following days: waxing moon (လဆန်း la hsan), full moon (လပြည့်နေ့ la pyei nei), waning moon (လဆုတ် la hsote), and new moon (လကွယ်နေ့ la kwe nei). The most common days of observance are the full moon and the new moon. In pre-colonial Burma, the Uposatha day (commonly rendered as the Buddhist Sabbath in English) was a legal holiday that was observed primarily in urban areas, where secular activities like business transactions came to a halt. However, since colonial rule, Sunday has replaced the Uposatha day as the legal day of rest. All major Burmese Buddhist holidays occur on Uposatha days, namely Thingyan, the beginning of the Buddhist lent (beginning in the full moon of Waso, around July to the full moon of Thadingyut, around October). During this period, Uposatha is more commonly observed by Buddhists than during the rest of the year. During Uposatha days, Buddhist monks at each monastery assemble and recite the patimokkha, a concise compilation of the Vinaya.

Mahayana countries

In Mahayana countries that use the Chinese calendar, the Uposatha days are observed ten times a month, on the 1st, 8th, 14th, 15th, 18th, 23rd, 24th and final three days of each lunar month. Alternatively, one can only observe Uposatha days six times a month; on the 8th, 14th, 15th, 23rd and final two days of each lunar month. In Japan, these six days are known as the roku sainichi (六斎日 Six Days of Fasting).

Names of Full Moon Uposatha Days

The Pali names of the uposatha days are based on the Sanskrit names of the nakśatra (Pali: nakkhatta), the constellations or lunar mansions through which the moon passes within a lunar month.

Full Moon Uposatha Day Names
Associated Month Pali Sanskrit Burmese Sinhala Thai Khmer Days
January Phussa Puṣya Pyatho(ပြာသို) Duruthu Pusaya (ปุศยะ) Bos (បុស្ស) 30
February Māgha Māgha Tabodwe(တပို့တွဲ) Navam Makha (มาฆะ) Meak (មាឃ) 29
March Phagguṇa Phalguṇa Tabaung(တပေါင်း) Medin (Maedhin) Pholkuni (ผลคุณี) Phagaun (ផល្គុន) 30
April Citta Chitrā Tagu(တန်ခူး) Bak Chittra (จิตรา) Chaet (ចេត្រ) 29
May Visākhā Viśākhā Kason(ကဆုန်) Vesak Visakha (วิสาขา) Vesak (ពិសាខ) 30
June Jeṭṭhā Jyeṣṭha Nayon(နယုန်) Poson Chetta (เชษฐา) Jais (ជេស្ឋ) 29/30
July Āsāḷhā Aṣāḍhā Waso(ဝါဆို) Esala (Aesala) Asarnha (อาสาฬหะ) Ashad (អាសាធ) 30
August Sāvana Śrāvaṇa Wagaung(ဝါခေါင်) Nikini Savana (สาวนะ) Srap (ស្រាពណ៍) 29
September Poṭṭhapāda Proṣṭhapāda/Bhādrapadā Tawthalin(တော်သလင်း) Binara Phattarapratha (ภัทรปทา) Phutrobot (ភទ្របទ) 30
October Assayuja Aśvayuja/Aśvinī Thadingyut(သီတင်းကျွတ်) Vap Assavani (อัศวนี) Asuj (អស្សុជ) 29
November Kattikā Kāṛttikā Tazaungmon(တန်ဆောင်မုန်း) Il Krittika (กฤติกา) Kadhek (កត្តិក) 30
December Māgasira Māṛgaśiras Natdaw(နတ်တော်) Unduvap Maruekasira (มฤคศิระ) Mekasay (មិគសិរ) 29


The word “uposatha” is derived from the Sanskrit word “upavasatha,” which refers to the pre-Buddhistic fast day that preceded sacrifices in the historical Vedic religion.

In the Buddha’s time, some ascetics used the new and full moon as opportunities to present their teachings. The Uposatha Day was instituted by the Buddha at the request of King Bimbisara, and the Buddha instructed the monks to give teachings to the laypeople on this day, and told the monks to recite the Patimokkha every second Uposatha day.


Lay practice

On each uposatha day, devout Upāsaka and Upāsikā practice the Eight Precepts, perhaps echoing the Buddha’s teaching that laypeople should “imitate” arhats on Uposatha days.

The Eight Precepts are modelled after the Ten Precepts observed by novice monks, except that the seventh and eighth precepts for the novices are combined, the ninth novice precept becomes the eighth, and the tenth novice precept (non-acceptance of gold and silver, use of money) is excluded as being impracticable for a lay person.

For lay practitioners who live near a vihara, Uposatha is an opportunity for them to visit it, make offerings, listen to dhamma talks by monks and participate in meditation sessions.

For lay practitioners unable to participate in the events of a local monastery, the uposatha is a time to intensify one’s own meditation and Dhamma practice, for instance, meditating an extra session or for a longer time, reading or chanting special Buddhist texts, recollecting or giving in some special way.

Monastic practice

On the new-moon and full-moon uposatha, in monasteries where there are four or more bhikkhus, the local Sangha will recite the Patimokkha. Before the recitation starts, the monks will confess any violations of the disciplinary rules to another monk or to the Sangha. Depending on the speed of the Patimokkha chanter (one of the monks), the recitation may take from 30 minutes to over an hour. Depending on the monastery, lay people may or may not be allowed to attend.

Communal reciprocity

Describing his experience of Uposatha day in Thailand, Khantipalo (1982a) writes:

“Early in the morning lay people give almsfood to the bhikkhus who may be walking on almsround, invited to a layman’s house, or the lay people may take the food to the monastery. Usually lay people do not eat before serving their food to the bhikkhus and they may eat only once that day…. Before the meal the laity request the Eight Precepts [from the bhikkhus] …, which they promise to undertake for a day and night. It is usual for lay people to go to the local monastery and to spend all day and night there…. [In monasteries where] there is more study, [lay people] will hear as many as three or four discourses on Dhamma delivered by senior bhikkhus and they will have books to read and perhaps classes on Abhidhamma to attend…. In a meditation monastery …, most of their time will be spent mindfully employed – walking and seated meditation with some time given to helping the bhikkhus with their daily duties. So the whole of this day and night (and enthusiastic lay people restrict their sleep) is given over to Dhamma….”

Special uposatha days

In Thailand five full-moon uposatha days are of special significance and are called puja:

  • Visakha Puja or Visakha Uposatha or Vesak (“Buddha Day”):

is the most sacred Buddhist holiday. It is the anniversary of the Buddha’s birth, awakening and parinibbana.

  • Asalha Puja or Asalha Uposatha. (“Dhamma Day”):
anniversary of the Buddha’s delivering his first discourse, which is collected as the Dhammacakkappavattana Sutta. The three-month-long Vassa retreat starts the following day.
  • Pavarana:
the end of the Rains Retreat residence during which time each monk atones before the Sangha for any offense they may have committed.
  • Anapanasati Day:

Anniversary of the Buddha’s delivering the “Anapanasati Sutta.” This event is not connected to an Uposatha (Poya) day in Sri Lanka and perhaps is particular to Thailand.

  • Magha Puja or Magha Uposatha. (“Sangha Day”):

Anniversary of the assembling of 1250 monks in the Buddha’s presence during which time he delivered the “Ovada-Patimokkha Gatha.”

In Sri Lanka, three full moon Uposatha or Poya days are of special significance.

  • Vesak Poya, which is described above.
  • Poson Poya corresponds to the Jeṭṭhā uposatha, which falls in June. It is of special significance in Sri Lanka because the Arahant Mahinda Thera, King Asoka’s son, officially introduced Buddhism to Sri Lanka on this day in the 3rd century B.C.
  • Esala Poya corresponds to Āsāḷhā uposatha, the full moon of July, and is described above. This day has special significance in Sri Lanka because it was the day that 56 nobles, headed by Prince Arițțha, became the first Sri Lankans to be fully ordained as a bhikkhus at Cetiyagiri in Mihintale by Mahinda Thera and his companions. It therefore marks the founding of the Lankan Bhikkhu Sangha.

In China and Vietnam, the Mid-Autumn Festival, Chuseok in Korea and Tsukimi in Japan center around the full moon Uposatha. All three festivals revolve around the Jataka tale of the Moon rabbit, known in China as the Jade Rabbit.

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