TL;DR: The Full Moon of the First Lunar Month (Tết Nguyên tiêu, lễ Thượng nguyên) is reckoned from the night of the 14th to the end of the 15th day of the first lunar month, so offering on either day falls within the festival. There is no mandatory hour; for families who follow the folk auspicious hours, in 2025 to 2030 the 15th is a Tý or Ngọ day with auspicious hours Tý, Sửu, Mão, Ngọ, Thân and Dậu. The offerings are usually two trays: vegetarian for the Buddha, savory for the ancestors. In 2027 the 15th falls on Saturday, 20 February.
What date is the Full Moon of the First Lunar Month, and when does it begin?
The Full Moon of the First Lunar Month is also called Tết Nguyên tiêu, and in Daoism it is called lễ Thượng nguyên[1]. By the common reckoning, the full moon day of the first lunar month is counted from the middle of the night of the 14th (the night before the full moon) to the end of the 15th (the night of the full moon) of the first lunar month[1]. Thus the festival period covers both the 14th and the 15th, not just one day.
For Vietnamese people, this is the first full moon of the new year, and the offerings made on it are taken very seriously[2]. Folk sayings have it: “Cúng cả năm không bằng Rằm tháng Giêng” (Offering all year is not equal to the Full Moon of the First Month) or “Lễ Phật quanh năm không bằng ngày rằm tháng Giêng” (Worshipping the Buddha all year is not equal to the full moon day of the first month)[1].
Why is there a choice between offering on the 14th or the 15th?
This choice arises from the understanding of the time span of the full moon day. Since the Full Moon of the First Lunar Month is counted from the night of the 14th to the end of the 15th[1], both times fall within the festival period. Offering guides also give both options: offering early on the 14th or on the main day, the 15th[1]. Many families offer in the late afternoon or evening of the 14th, the night before the full moon, seeing it as the start of the festival; others offer in the morning or at noon of the 15th.
Some Buddhist texts explain that on the Full Moon of the First Lunar Month the light of the Buddha's compassion has strong power and shines universally over the human realm[1].
What hour is reasonable for offering on the Full Moon of the First Lunar Month?
No ritual text sets a mandatory hour of offering for every family. Some offering guides advise choosing an hour that suits the heavenly stem and earthly branch of the festival day[1], that is, choosing by the auspicious hours (giờ hoàng đạo) of day selection. In practice, some families offer on the morning of the 15th, others in the late afternoon or evening of the 14th or the evening of the 15th.
The 14th and 15th days of the first lunar month in 2025 to 2030, converted to the Gregorian calendar in Vietnam time, with the stem-branch (can chi) of each day:
| Lunar year | 14th of the first month | 15th of the first month | Can chi of the 14th | Can chi of the 15th |
|---|---|---|---|---|
| Ất Tỵ 2025 | Tuesday, 11 February 2025 | Wednesday, 12 February 2025 | Tân Hợi | Nhâm Tý |
| Bính Ngọ 2026 | Monday, 2 March 2026 | Tuesday, 3 March 2026 | Ất Hợi | Bính Tý |
| Đinh Mùi 2027 | Friday, 19 February 2027 | Saturday, 20 February 2027 | Kỷ Tỵ | Canh Ngọ |
| Mậu Thân 2028 | Tuesday, 8 February 2028 | Wednesday, 9 February 2028 | Quý Hợi | Giáp Tý |
| Kỷ Dậu 2029 | Monday, 26 February 2029 | Tuesday, 27 February 2029 | Đinh Hợi | Mậu Tý |
| Canh Tuất 2030 | Friday, 15 February 2030 | Saturday, 16 February 2030 | Tân Tỵ | Nhâm Ngọ |
Under the folk table of auspicious hours, the auspicious hours follow the earthly branch of the day. In all six years above, the 14th is a Hợi or Tỵ day, with auspicious hours Sửu (1-3am), Thìn (7-9am), Ngọ (11am-1pm), Mùi (1-3pm), Tuất (7-9pm) and Hợi (9-11pm); the 15th is a Tý or Ngọ day, with auspicious hours Tý (11pm-1am), Sửu (1-3am), Mão (5-7am), Ngọ (11am-1pm), Thân (3-5pm) and Dậu (5-7pm).
What does the offering tray for the Full Moon of the First Lunar Month include?
Offering guides usually divide the offerings into two trays: one for the Buddha and one for the ancestors[1]. The Buddha tray is vegetarian, with incense, flowers, tea, five fruits, xôi gấc, chè trôi nước and vegetable dishes, and nothing savory may be placed on the Buddha altar[1]. The ancestor tray is savory, typically "4 bowls, 6 plates": bamboo shoot stew, mọc meatballs, glass noodles and bóng pork skin, together with boiled chicken, giò chả, fried spring rolls, pickled onions and bánh chưng[1].
| Type of tray | Common components | Note |
|---|---|---|
| Buddha tray | Incense, flowers, tea, five fruits, xôi gấc, chè trôi nước, vegetables | Vegetarian, nothing savory |
| Ancestor tray | Bamboo shoot stew, mọc, glass noodles, bóng; boiled chicken, giò chả, fried spring rolls, pickled onions, bánh chưng | Savory, "4 bowls, 6 plates" |
What is noteworthy in the prayer text for the Full Moon of the First Lunar Month?
The prayer texts in circulation today often begin with a invocation to the Buddha, then pay respects to deities such as Hoàng thiên, Hậu Thổ, chư vị Tôn thần, Bản gia thổ địa Long Mạch, Ngũ phương, Ngũ thổ, Phúc đức Tông thần, Tiền hậu địa chủ tài thần[2]. Next comes the declaration of name, age, residence, and the prayers.
In the preface of Gia lễ giản yếu (1932), Dương Bá Trạc writes that ritual texts and prayers used to be written entirely in Chinese characters, and family genealogies were also recorded in Chinese characters; he wrote ready-made prayers in quốc ngữ so that everyone, educated or not, could copy them[4]. In its section Lễ tết, the same book lists thượng nguyên, that is, the Full Moon of the First Lunar Month, among the "meaningless" seasonal festivals that should be dropped, keeping only Tết Nguyên đán, Thanh minh and cơm mới[4].
Should one offer on both the 14th and the 15th?
Offering on both days is not obligatory, but it is not considered wrong either. Besides the offering at home, many people also go to pagodas and temples[1], and many pagodas hold prayers for peace on the full moon day itself[2]. So some families make the ancestor offering at home on the evening of the 14th and go to the pagoda on the 15th.
Common misunderstandings about the offering day
The first misunderstanding is that only the 15th is sacred, while the festival period is counted from the night of the 14th[1]. The second is that offering outside the auspicious hours is wrong: auspicious hours are a rule of day selection, not a condition set by the ritual.
Hiệp kỷ biện phương thư, the day-selection manual compiled under the Qing court, likewise does not treat days and hours as the source of fortune. Its General Discussion in volume 3 notes that Wang Chong, in the Lunheng, spared no effort attacking day selection, yet calls him a pedantic scholar; it endorses Xun Yue's words in the Shenjian, 「此天地之數也非吉凶所從生也」, meaning these are the numbers of Heaven and Earth, not the source of good or ill fortune, and adds that one who knows they are the numbers of Heaven and Earth should follow them in cultivating oneself.
Practical suggestions from Nhật Nguyệt
Nhật Nguyệt's suggestion: if the family is busy, they may offer to the ancestors in the late afternoon or evening of the 14th and go to the pagoda on the 15th; if they wish for a full family gathering, they may offer in the morning or at noon of the 15th. The offering tray need not be elaborate; what matters is careful preparation and sincerity. For those far from home, they may light incense to remember the ancestors during the festival period, without necessarily being present at home.
Frequently asked questions
What solar date is the Full Moon of the First Lunar Month this year?
The date changes with each lunar year. The Full Moon of the First Lunar Month fell on Wednesday, 12 February 2025 in the year Ất Tỵ[2] and on Tuesday, 3 March 2026 in the year Bính Ngọ[3]; in the year Đinh Mùi it falls on Saturday, 20 February 2027. The years up to 2030 are in the table in the section on offering hours above.
Does offering on the Full Moon of the First Lunar Month need to be at an auspicious hour?
There is no mandatory rule. Some guides advise choosing an hour that suits the stem-branch of the festival day[1], but auspicious hours are a rule of day selection. For families who wish to follow them, in 2025 to 2030 the 15th of the first month is a Tý or Ngọ day, with auspicious hours Tý, Sửu, Mão, Ngọ, Thân and Dậu.
Is it necessary to offer both a vegetarian tray and a savory tray?
Not necessarily. Guides keep the Buddha tray vegetarian, with nothing savory, and make the ancestor tray savory[1]. A household without a Buddha altar needs only the ancestor tray.
