Vietnamese calendar

Vietnamese calendar
Name	Vietnamese calendar
Other names	Âm lịch, Lịch âm
Type	Lunisolar calendar
Region	Vietnam
Epoch	Traditional East Asian epochs
Months	12 or 13 lunisolar months
Intercalation	Leap month system
Related	Chinese calendar, Japanese calendar, Korean calendar, Mongolian calendar

Vietnamese calendar

The Vietnamese calendar is a traditional lunisolar system used historically in Vietnam for civil, agricultural, and ritual purposes, sharing roots with the Chinese calendar and reflecting exchanges with China and regional polities such as Dai Viet and Nguyen dynasty. It integrates astronomical observables with indigenous practice and informs festivals, imperial ceremonies, and agricultural timetables linked to dynasties like the Ly dynasty, Tran dynasty, and Le dynasty.

Overview and history

The calendar evolved during periods of Chinese influence, administrative reform, and local adaptation across eras including the Tang dynasty interaction, the Song dynasty tributary relations, and the autonomy of Dai Viet under rulers such as Ly Thai To and Le Loi. Monarchs in the Nguyen dynasty standardized era names and calendrical pronouncements; scholars like court astronomers under Gia Long and Minh Mang managed computations. Contacts with European missionaries and scientists associated with names like Alexandre de Rhodes and institutions such as Jesuit China missions introduced Western calendrical ideas that influenced later reforms during the French colonization of Vietnam and the republican transitions culminating in comparisons to the Gregorian calendar.

Structure and components

Months follow lunar phases with each month beginning on the new moon, aligned to solar terms inherited from the Twenty-four solar terms system used in China and adopted regionally by Vietnamese court astronomers. The calendar uses sexagenary cycles combining the heavenly stems and earthly branches (the Ganzhi system) to denote years, months, days, and hours, paralleling East Asian practice recorded in court annals and inscriptions in places such as Thang Long Imperial Citadel. Zodiacal animals used in popular culture correspond to the Chinese zodiac but show local variants in folk uses recorded in provincial chronicles of Tonkin and Cochinchina. Official proclamations from the Imperial Examination bureaucracy and chronologies in the Dai Viet Su Ky Toan Thu relied on these components.

Lunisolar calculations and intercalation

Astronomical calculation for intercalation matches lunisolar logic where a leap month is inserted to keep months synchronized with solar terms like Dongzhi and Xiazhi; Vietnamese computations historically referenced methods from the Shoushi calendar and other Chinese calendrical manuals transmitted via tributary and scholarly exchanges. Court astronomers used ephemerides and methods similar to those in the Yuan dynasty and Ming dynasty astronomical treatises; later, Western astronomical techniques encountered through figures such as Jean-Baptiste Bourguignon d'Anville and missionary astronomers prompted technical reassessment. Intercalary months were determined by the absence of a principal term within a lunar month, a rule paralleling decisions documented in the Treatise on Astrology of the Kaiyuan era circulating in East Asia. Regional observatories and scholars in Hue and Hanoi maintained almanacs for agricultural and ritual scheduling.

Cultural and religious significance

The calendar governs major religious observances and ancestral rites tied to temples like Temple of Literature and One Pillar Pagoda, and to festivals associated with deities honored in institutions such as Bac Lieu Temple and village communal houses. Ritual calendars coordinate with practices in Caodaism communities, Buddhist monasteries including Thien Mu Pagoda, and Taoist-influenced ceremonies, while Confucian ritual timings were codified in court protocols under dynastic rulers. Zodiacal attributions affect naming practices, marriage selection, and divination traditions maintained by folk practitioners and astrologers recorded in colonial ethnographies by scholars engaging with Tonkinese village life.

Holidays and observances

Primary observances anchored in the lunisolar system include Tết (Lunar New Year), the Mid-Autumn Festival, and seasonal festivals tied to rites such as the Hungry Ghost Festival; these events are linked to agricultural cycles observed in rice-growing regions like the Mekong Delta and Red River Delta. Imperial ceremonies such as the royal cung nghinh processions and sacrifices at the Temple of Literature followed calendrical dates, while local festivals—Lim Festival, Perfume Pagoda Festival, and Huong Pagoda pilgrimages—use the traditional months and days for scheduling. Commemorations of historical events recorded in annals, such as anniversaries of victories by figures like Tran Hung Dao or Nguyen Hue (Quang Trung), were sometimes set by lunisolar dates.

Modern usage and reforms

With the 20th-century adoption of the Gregorian calendar in official civil administration under colonial and republican regimes, lunisolar usage shifted to cultural, religious, and agricultural domains, while state institutions in Hanoi and Ho Chi Minh City coordinate public holidays using Gregorian dates supplemented by lunisolar calculations for festivals. Reforms and standardization efforts interacted with modern observatories, the Institute of Astronomy and Geophysics, and international timekeeping standards maintained by agencies such as International Astronomical Union and Bureau International des Poids et Mesures influences. Contemporary practice blends traditional almanacs produced by publishers and scholarly work at universities like Vietnam National University with global calendrical systems used in commerce and diplomacy.

Category:Calendars