The lunar calendar in Vietnamese life

Vietnamese life runs on two calendars: the Western solar calendar for work and school, and the lunar calendar, âm lịch, for holidays, religious days and family rituals. The lunar calendar decides when Tết falls, when people visit pagodas and when families mark a relative's death anniversary.

Here is how it works and where you will notice it.

What is âm lịch?

Âm lịch ("um lik") means "lunar calendar," and dương lịch ("zuh-ung lik" in the North, "yuh-ung lik" in the South) means "solar calendar." Strictly speaking, the Vietnamese traditional calendar is lunisolar: months follow the moon, but extra months are added now and then so the year stays roughly in step with the seasons.

• Each month starts on the day of the new moon.
• The full moon falls around the 15th of each month.
• A lunar month has 29 or 30 days.
• A normal lunar year has 12 months, about 354 days.
• About seven times in every 19 years, an extra leap month (tháng nhuận) is added.

That is why Tết moves around on the Western calendar, landing somewhere between late January and mid-February.

How do people say lunar dates?

Days 1 to 10 of a lunar month are called mùng ("moong") plus the number: mùng 1, mùng 2 and so on. After that, people just use the number. The 15th is also called rằm ("rum"), the full-moon day.

The first lunar month is tháng Giêng ("tahng zyeng"), and the last is tháng Chạp ("tahng chahp"). So Rằm tháng Giêng is the first full moon of the year.

Many Vietnamese wall calendars show both dates on every page, with the solar date in large print and the lunar date in smaller type. Tear-off daily calendars that do this are a common sight in homes and shops.

Where does the lunar calendar show up?

Holidays. The biggest festivals are set by lunar date:

• Tết Nguyên Đán: the 1st day of the 1st month. In 2027 that is February 6. See what Tết is.
• Ông Táo: the 23rd of the 12th month, when families send off the Kitchen Gods.
• Hung Kings Commemoration: the 10th of the 3rd month.
• Tết Trung Thu: the Mid-Autumn Festival on the 15th of the 8th month.

Mùng 1 and Rằm. On the 1st and 15th of each lunar month, many families light incense, place fruit and flowers on the altar and visit pagodas. Some people eat vegetarian on these days.

Death anniversaries. A family's đám giỗ, the yearly remembrance of a relative who has passed, is held on the lunar date of their death. It is one of the most important family gatherings outside of Tết.

Choosing good days. Some families consult the lunar calendar or an expert when choosing dates for weddings, moving house, opening a business or starting construction. Practices vary widely; some families take it seriously, others not at all.

What about the zodiac?

Each lunar year carries a name from a 60-year cycle that combines ten heavenly stems with twelve earthly branches. The branches are linked to the 12 zodiac animals. The year that begins on February 6, 2027 is Đinh Mùi, the Year of the Goat.

Vietnam's zodiac matches China's except for one animal: Vietnam has the Cat (Mão, also written Mẹo) where China has the Rabbit. See the Vietnamese zodiac: 12 animals and what they mean.

Is the Vietnamese lunar calendar the same as the Chinese one?

They are based on the same system, but Vietnam calculates its calendar using its own time zone, UTC+7, while China uses UTC+8. Most years this makes no difference. Occasionally the one-hour gap shifts a new moon across midnight, so a month, or even Tết itself, can start on a different day in the two countries.

Do people still use it day to day?

For most practical things, such as work schedules, school terms and appointments, Vietnam uses the solar calendar. The lunar calendar lives alongside it for culture and family life. Older relatives may remember birthdays by lunar date, and many people know their lunar birth year animal well, even if they do not track lunar dates otherwise.

A quick guide for beginners

• Tết is always the 1st of the 1st lunar month.
• Rằm is the 15th, the full moon.
• Mùng 1 and Rằm are common days for offerings.
• Death anniversaries follow the lunar date.
• Leap months keep the calendar in line with the seasons.

If you want to follow along, install a calendar app or buy a wall calendar that shows lunar dates; within a month you will start noticing the full-moon days everywhere.