Tết Nguyên Đán dates, 1901–2099

The first day of the Vietnamese lunisolar year, in Gregorian dates, computed on the meridian Vietnam uses rather than the one China uses. Usually this is the same day as Chinese Lunar New Year. In 7 years out of 199 it is not.

Why Vietnam and China can disagree

Both calendars are built the same way. A month begins on the day of a new moon; the year begins at the second new moon after the winter solstice; a thirteenth month is inserted in the years that need one to keep the months in step with the sun. Neither calendar rounds a new moon to the nearest day — it belongs to whichever civil day it happens to fall in.

That last point is where the two part company. Vietnam computes against the meridian 105° East and China against 120° East, an hour apart. A new moon at half past midnight in Beijing is at half past eleven the previous evening in Hanoi, and the month begins on different days in the two countries. Most of the time this changes nothing anyone notices. Occasionally it moves the boundary of the month that has to contain the winter solstice, and then it moves the whole intercalation — a thirteenth month lands in a different year, and Tết arrives a month away from Lunar New Year.

1985 is the one that matters to people rather than to calendars. Vietnam saw in the year of the Ox on 21 January; China saw it in on 20 February. Anyone born in Vietnam in that month is an Ox at home and a Rat in every zodiac lookup that assumes the Chinese calendar — which is most of them.

The years Vietnam was divided

North Vietnam moved its calendar to the 105° East meridian in 1967. The South went on following the Chinese calendar until reunification, so for several years the country kept two calendars at once, and twice — in 1968 and 1969 — they disagreed about which day the year began on.

The best known consequence is a matter of historical record rather than of arithmetic: Tết 1968 began on 29 January in Hanoi and 30 January in Saigon. The dates in the table above are the Northern ones throughout, because that is the calendar the unified state kept. For a birth in the South between 1968 and 1975, the dates on the Chinese table are the ones that were observed.

How to read this table

Tết falls between 21 January and 21 February, and everything that keys off the year turns on that date rather than on 1 January — the can chi year, the zodiac animal, and the day a person's tuổi mụ goes up. Someone born on 10 February 2026 was born a week before Tết, which makes them Ất Tỵ and not Bính Ngọ.

Leap months

Twelve lunar months fall about eleven days short of a solar year, so roughly every third year gains a thirteenth. It repeats the number of the month before it — a leap month after month 2 is a second month 2, not a month 13. Of the 199 years in this table, 73 have one.

The zodiac animals

Vietnam's twelve animals are not quite China's. The fourth branch, Mão, is the cat in Vietnam and the rabbit in China; the second, Sửu, is the water buffalo rather than the ox. The can chi names in this table are the branch names themselves, which the two traditions share, so nothing here depends on which animal a reader assigns to them.