Đoan Ngọ Festival, 5th of the fifth lunar month

Đoan Ngọ is a Sino-Vietnamese name: "đoan" means beginning and "ngọ" is the noon hour, the middle of the day. The festival falls on the fifth day of the fifth lunar month, and the fifth month is also the month of the Horse in the stem-and-branch calendar, so the day is also called Trùng Ngũ, the double fifth, or Đoan Dương. It sits close to the summer solstice, when the sun is highest, the heat is fierce and thunderstorms begin.

People long ago noticed that midsummer is when illness spreads most easily and pests multiply, damaging crops and harming health. Đoan Ngọ therefore became a day of "cleansing" for the whole community: people eat sour, spicy and fermented foods to purify the body, while farmers give thanks to heaven and earth after the spring rice harvest has just been brought in.

Folk tales say that long ago, after a bountiful harvest, villagers were celebrating when swarms of pests arrived and stripped the crops and orchards bare. As everyone despaired, an old man appeared from nowhere, called himself Đôi Truân and told them to set up an altar, lay out ash cakes and fruit, and exercise together early in the morning.

They did as he said, and soon the pests dropped dead. When the villagers wanted to thank him he had already gone, leaving only the advice to repeat the rite every fifth day of the fifth month to protect crops and health. Since then Vietnamese people have called it the pest-killing festival, eating fermented rice and sour fruit first thing in the morning before anything else.

In China the festival is tied to Qu Yuan, poet and minister of the state of Chu in the Warring States period, who lived around the fourth and third centuries BCE. He wrote the famous long poem Li Sao. Slandered and exiled for remonstrating with the king, on learning that the Chu capital had fallen in 278 BCE he clasped a stone and drowned himself in the Miluo River on the fifth day of the fifth month.

Legend has it that people rowed out to search for his body and threw leaf-wrapped rice into the river so the fish would not eat it. From this came dragon boat racing and eating rice dumplings on the day. In 2009 UNESCO inscribed China's Dragon Boat Festival on the Representative List of the Intangible Cultural Heritage of Humanity, and in 2005 Korea's Gangneung Danoje Festival had been inscribed as well.

The road ahead is long and far, and I will search high and low.

Qu Yuan, Li Sao

Though it shares the date with China, the Vietnamese festival is not tied to Qu Yuan and has almost no dragon boat racing. It is bound to the rhythm of wet-rice farming: giving thanks after the spring crop, praying for the next one and killing pests both in the fields and in the body. The food is village food too, made from glutinous rice, orchard fruit and the plants that grow around the house.

Many customs are distinctly local. Adults pick medicinal leaves at the noon hour, believing that is when plants are at their best, then dry them to brew tea for the whole year. Children have their fingernails dyed with henna leaves, wear five-coloured threads on their wrists to ward off evil and wish for a healthy summer. In many villages people bathe in herbal water and smoke the house with mugwort and pomelo leaves to cleanse it.

Each region has its own offering tray. The north eats fermented golden sticky rice, ash cakes, plums and lychees. The centre, especially Huế, has duck, millet sweet soup and leaf-wrapped dumplings. The south eats ash dumplings, fermented rice balls and orchard fruit such as mango, rambutan and mangosteen. These differences show that each region of Vietnam has made Đoan Ngọ its own.

Today, even in the city, many families still eat fermented rice and fruit on the morning of the fifth. Traditional markets and supermarkets sell fermented rice, ash cakes, Hà Nội plums and Lục Ngạn lychees for days beforehand. Đoan Ngọ is not a public holiday, so many people eat a quick bowl of fermented rice before work or bring a box to the office to share with the team.

For those working far from home, Đoan Ngọ is a moment to call home, ask whether Mum is making fermented rice this year, or send a basket of first fruits to the grandparents. Many companies use the day for a small lunch or hand out fermented rice and fruit to staff, keeping a cultural tradition alive and creating a pleasant pause in the middle of the year.