The Yulanpen Sutra, also known as the Ullambana Sutra(Chinese: 盂蘭盆經; pinyin: yú lán pén jīng; Japanese pronunciation: urabon-kyō; Korean: 우란분경; Vietnamese: Kinh Vu Lan Bồn), is a Mahayanasutra concerning filial piety. It was translated from an Indic language (see History) and is found in Taisho 685 and Taisho 686 in Volume 16, the third volume of the Collected Sutra Section. Taisho 685 was translated by Dharmarakṣa from 265-311 CE  and is entitled: ‘The Buddha Speaks the Yulanpen Sutra’. Taisho 686 was translated by an unknown or lost translator during the Eastern Jin Dynasty and is entitled: ‘The Buddha Speaks the Sutra of Offering Bowls to Repay Kindness’. According to Karashima, Taisho 686 is basically a more idiomatic adaptation of Taisho 685. It records the events which followed after one of the disciples of Shakyamuni Buddha, Maudgalyayana, achieves Abhijñā and uses his newfound powers to search for his deceased parents. In the end, Maudgalyayana finds his mother in the preta (hungry ghost) world and with the assistance of the Buddha, is able to save her. The East AsianGhost Festival is based on this sutra.
The Yulanpen Sutra has traditionally been regarded as being translated from the Sanskrit into Chinese by Dharmarakṣa under the Jin at some point between 265-311 CE The subject matter of the Yulanpen Sutra is broadly similar to several accounts described in other sutras. The most ancient of those accounts (Petavatthu No. 14 - The Story of the Mother of Sariputta) describes how the disciple Sāriputta rescued his mother (from five past lives ago) who had become a preta or hungry ghost. Similar to the Yulanpen Sutra, Sariputta builds four huts and fills them with food and drink for the Sangha of the four quarters; with the Buddha present, he dedicates this donation on behalf of his suffering mother. The transference of merit enables Sariputta's mother to be reborn and released from the preta world. Another account can be found in Avadanasataka which is also very similar to the Yulanpen Sutra, Maudgalyayana communicates on the behalf of five hundred pretas with their relatives who make offerings on the pretas' behalf to the monastic community. Once the transference of merit is completed, the former pretas are reborn and release from their suffering.
The sutra records the time when Maudgalyayana achieves abhijñā and uses his new found powers to search for his deceased parents. Maudgalyayana discovers that his deceased mother was reborn into the preta or hungry ghost realm. She was in a wasted condition and Maudgalyayana tried to help her by giving her a bowl of rice. Unfortunately as a preta, she was unable to eat the rice as it was transformed into burning coal. Maudgalyayana then asks the Buddha to help him; whereupon Buddha explains how one is able to assist one’s current parents and deceased parents in this life and in one’s past seven lives by willingly offering food, etc., to the sangha or monastic community during Pravarana (the end of the monsoon season or vassa), which usually occurs on the 15th day of the seventh month whereby the monastic community transfers the merits to the deceased parents, etc.,
^Both Taisho 685 and 686 are found in Volume 16 of the Taisho Tripitaka."Taishō Shinshū Daizōkyō" 大正新脩大藏經 [Taishō Shinshū Tripitaka]. CBETA 漢文大藏經 (in Chinese). This is an index to the Taisho Tripitaka - nb Volume 16 is listed as 經集部 or Collected Sutra Section; it is where Taisho 685 (The Buddha Speaks the Yulanpen Sutra) and Taisho 686 (The Buddha Speaks the Sutra of Offering Bowls to Repay Kindness) are located.
^辛嶋静志 Karashima Seishi (October 2013). 「盂蘭盆」の本当の意味 ―千四百間の誤解を解く [The Real Meaning of Urabon [Yulanpen] –The Solution to a 1400 Year Misunderstanding]. 大法輪 (The Great Wheel of the Dharma) (in Japanese): 182. ほぼ同じ内容の「報恩奉盆経」という経典ものあるがこれは前者がいかにも直訳だったものを中国的に改めたものにすぎない。(see text for translation)CS1 maint: Uses authors parameter (link)
^Karashima Seishi (March 2013). "The Meaning of Yulanpen 盂蘭盆 "Rice Bowl" On Pravāraṇā Day"(PDF). Annual Report of The International Research Institute for Advance Buddhology at Soka University for the Academic Year 2012. XVI: 289,301,302. p.302 -Although this sutra has often been regarded as apocryphal [Japanese version has in recent times], the contents and ideas in it are well rooted in India as we have seen above. In addition to that, the vocabulary and usage of Chinese words are more archaic, compared with Kumārajīva's corpus (401-413 CE), while they resemble greatly the translations by Dharmarakṣa (fl. 265?-311 CE). Moreover, the transliteration 鉢和羅 (EH pat γwa la > MC pwât γwâ lâ} of Skt. pravāra(ṇā), which only occurs in this sutra and its adaptation, i.e. the Baoen Fengpen jing 報恩奉盆經 (T. 16, no. 686, 780a20), indicates clearly that this sutra is not apocryphal but a genuine translation, because only somebody who knew the original Indian form was able to transliterate it thus correctly into Chinese. In conclusion, I assume [<-missing in Japanese version] that this sutra is not apocryphal, but a translation from an Indian text translated by Dharmarakṣa or somebody else in pre-Kumārajīva times [Japanese version has 3rd to 4th century CE]. [c.f. p 189 for equivalent in Japanese version] Also c.f. p 301 for derivation of Yulan from Middle Indic (Gandhari) *olana.CS1 maint: Uses authors parameter (link)
^Karashima Seishi (March 2013). "The Meaning of Yulanpen 盂蘭盆 "Rice Bowl" On Pravāraṇā Day"(PDF). Annual Report of The International Research Institute for Advance Buddhology at Soka University for the Academic Year 2012. XVI: 297–8.CS1 maint: Uses authors parameter (link) Also Sanskrit fragments of this account have been found.
^辛嶋静志 Karashima Seishi (October 2013). 「盂蘭盆」の本当の意味 ―千四百間の誤解を解く [The Real Meaning of Urabon [Yulanpen] –The Solution to a 1400 Year Misunderstanding]. 大法輪 (The Great Wheel of the Dharma) (in Japanese): 185. 東南アジアの盂蘭盆と東アジアのワン・オ一クパンサーなどは、いずれも、釈尊の時代に規定された様に七月十五日の自恣の日を祝っているのだが（日本ではこのことはすでに意識されていない）、東南アジアでは古代インドの暦に基づいて行われるのに対し、東アジアでは、中国の太陰暦に従っているので、ニケ月の差があり、これらが同一の行事ということに気付く人は少ない。English Translation: Both the East Asian Urabon [Yulanpen] and Southeast Asian Wan Ok Phansa [Thai name for Pravāraṇā] are celebrated on the 15th day of the seventh month, the day of Pravāraṇā just as it was promulgated in Lord Buddha's time (in Japan, this matter is not known to people). In Southeast Asian countries, they use the ancient Indian calendar [or Buddhist calendar] as opposed to East Asian countries where they use the Chinese calendar. As there is a two month difference between the two calendars, few people realized that the two are [in fact] the same event.CS1 maint: Uses authors parameter (link)
^Karashima Seishi (March 2013). "The Meaning of Yulanpen 盂蘭盆 "Rice Bowl" On Pravāraṇā Day"(PDF). Annual Report of The International Research Institute for Advance Buddhology at Soka University for the Academic Year 2012. XVI: 293. Pravāraṇā (Pāli Pavāraṇā) zizi 自恣 and suiyi 隨意 in Chinese, is a ceremony held at the end of the three-month rainy season retreat [also called vassa] by Buddhist monks. In Theravada Buddhism and in Nepal, it was and is still held on the full moon day of the seventh or eight month. i.e. Āśvina (September–October) or Kārttika (October–November) respectively.CS1 maint: Uses authors parameter (link)
^辛嶋静志 Karashima Seishi (in Chinese -辛島靜志) (February 2014). Translated by 裘雲青 (Qiu Yunqing). 盂蘭盆之意-自恣日的“飯鉢” [The Meaning of Yulanpen 盂蘭盆 "Rice Bowl" On Pravāraṇā Day]. 中華文史論叢 (title tr. to English - Journal of Chinese Literature and History) (in Chinese) (114): 286. 對佛教徒來說，自古印度年曆（元旦相當於公曆三月中至四月中）四月十五日（公曆六至七月）或五月十五日（公曆七至八月）開始的三個月是雨安居。直至今天，西藏、尼泊爾、東南亞地區的僧人依然在此期間行雨安居。這一習俗也傳到沒有雨季的中國大陸中原地域，年曆和數字被原封不動地保留下來，但由印度年曆變為中國太陰曆。在中國、日本、朝鮮半島等東亞地區，雨安居從陰曆四月（公曆五月）開始，持續三個月。English Translation: From the Buddhist viewpoint, based on the Ancient Indian calendar [or Buddhist calendar] (New Years is in the middle of March to the middle of April [in the Gregorian calendar]) the 15th day of the fourth month [Āṣāḍha] (June to July [in the Gregorian calendar]) or the 15th day of the fifth month [Śrāvaṇa] (July to August [in Gregorian calendar]) is the start of three month period called vassa. From ancient times to even today, the monastic community of Tibet, Nepal and Southeast Asia still follow this schedule to observe vassa. This custom was also transmitted to China which does not have a rainy season, the calendar and dates preserved unchanged from the original but instead of using the ancient Indian calendar, the lunar Chinese calendar is used. In China, Japan, the Korean peninsula and other East Asian regions, vassa starts on the fourth month of the lunar Chinese calendar (May (in the Gregorian calendar) and lasts 3 months. [n.b. Since the start of vassa is fixed in East Asia in the fourth month, Pravāraṇā is also fixed to the 15th day of the seventh month].CS1 maint: Uses authors parameter (link)
Bandō, Shōjun, ed. (2005), "The Ullambana Sutra (Taishō Vol. 16, No. 685)", Apocryphal Scriptures(PDF), Bukkyō Dendō Kyōkai English Tripitaka Series, Berkeley: Numata Center for Buddhist Translation and Research, pp. 17–44, ISBN1-886439-29-X.