How Did Ancient Vietnamese Measure the Hours of the Day?

According to the Vietnamese Imperial Court of Khâm Thiên, the lunar calendar, seasons, and hours were previously organized (with slight adaptations from Chinese traditions) so that fortune tellers and astrologers could conduct their practices accordingly. There are 12 hours based on the 12 zodiac animals, corresponding to a 24-hour clock:

Now, let’s explore the phrase “Night of Five Watches, Day of Six Periods.” “Night of Five Watches” corresponds to 10 hours, starting from:

Meanwhile, “Day of Six Periods” corresponds to 14 hours and 7 periods according to the lunar calendar (Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster), starting from 5 AM (beginning of the Rabbit Hour) to 7 PM (beginning of the Dog Hour). Therefore, each “period” corresponds to how many hours and minutes (14/6=?). To this day, no one has clearly analyzed this. And since no one has taken the time to discuss, supplement, or clarify, the concept of “period” remains as ambiguous as the night of the thirtieth.

Soldiers beating drums to signal the time in the ancient Imperial City of Hue.

Scholar Hoàng Xuân Hãn believes that: A “period” is 1/100 of a day, meaning 1 period is equivalent to 14 minutes and 24 seconds of Western time.

Scholar Đào Duy Anh argues that every 15 minutes is 1 period (equivalent to 1/4 hour).

The compiler of the Thanh Nghị dictionary explains that: a period is 1/6 of daytime, meaning one period is equivalent to 2 hours and 20 minutes.

The Vietnamese Language Dictionary, Institute of Linguistics, edited by Hoàng Phê (Social Science Publishing House, 1988) combines both definitions: “period = 1/4 hour” and “equal to 1/6 of daytime” (not specifying the time frame).

However, many people do not fully agree with the aforementioned viewpoints, based on the reasoning: “There are 5 watches at night, from the First Watch to the Fifth Watch (from 7 PM to 5 AM). There are 6 periods during the day, from 5 AM to 5 PM (which is 12 hours), and the time from 5 PM to 7 PM (Rooster Hour) doesn’t need to be counted (as it is a time that is neither day nor night, when the gongs and drums signal the soldiers to close the city gates), so there’s no need for hours or periods at all!”

But some argue back: The time from 5 AM to 7 AM is also a transitional period between “Night and Day”, so why should it be classified into one of the 6 periods?

Now, returning to the traditional way of telling time, during the night, the five watches are indicated by the sound of drums (or wooden clappers) at the watchtower. One drumbeat for the First Watch, two for the Second Watch… until the Fifth Watch, which is marked by five drumbeats at 3 AM. This concludes the night watch’s duty; after the Fifth Watch, from 5 AM to 7 AM is the rooster’s free time, where it can crow as much as it wants, without anyone prohibiting it from signaling the time for humans, crowing to greet a new day, to attract hens, or just to compete with other roosters (one rooster’s crowing will elicit responses from many others).

After that, farmers along with their oxen head to the fields to work, leading to the following poem from the Kinh Thi:

The sun rises, then we work

The sun sets, then we rest…

Interpreted as:

When the sun rises, we work

When the sun sets, we rest

Plow the fields to eat

Dig wells to drink

The king’s authority means nothing to us.

Next, noon is at 12 PM, when the shadow of the tree is at its shortest. By looking at the shadow of the tree, one can tell the time, take a break for a meal, and when the shadow starts to tilt slightly, it indicates that the Goat Hour has passed, and work resumes until the sound of the gong from the military camp signals the start of the Rooster Hour (around 5 PM to 7 PM), when people and their oxen return home, and the roosters go back to their coops. Our farmers have lived this way for thousands of years without needing to buy a clock. At night, the watchtowers would mark time on a post outside, and the watchmen would look at the evening star to determine the time and sound the drum or clapper.

At midnight, the sound of mice scurrying indicates it is indeed the Rat Hour of the Third Watch, without any error. During nearly a hundred years of French colonialism, in addition to the traditional watches and periods, our people also had another way to tell time: around 5 AM, the French soldiers would play a bugle (known as the “rallying bugle”), and the bugler would sound: “The Ox pulls the cart, The cart pulls the Ox…”. The people would know immediately that it was time to wake up, calling the Green Uniform soldiers to do exercises (wash up and have breakfast). Around 5 PM, there would be another bugle call: “Let our soldiers go home, let our soldiers eat…”.

Timekeeping Tools of Ancient East Asians

Gnomon (Shadow Measuring Tool)

This was created from a horizontal rod – “gnomon” and a vertical rod – “measuring tool”. The measuring tool is placed perpendicular to the gnomon to measure the length of the sun’s shadow. Thus, not only can time be estimated, but one can also determine the seasonal changes based on the length of the sun’s shadow in the morning.

Sun Dial

The Sun Dial, also known as “sun measure,” is a tool that determines time through observing the shadow cast by the sun. It consists of a gnomon and a circular plate, with 24 evenly spaced divisions carved on the plate. The gnomon is placed perpendicular at the center of the plate. By observing the shadow of the gnomon pointing to these divisions, one can determine the time.

Water Clock

The water clock is a tool that judges time based on the amount of water, capable of measuring time in all weather, thus compensating for the shortcomings of the sun dial. This was a timekeeping tool highly valued by ancient Chinese.

The water clock is divided into two parts: a small water container and a receiving container. The small water container is divided into 2 to 4 tiers, each with small holes to allow water to drip. The final drip flows into the receiving container, which has a vertical pointer marked with 100 divisions. As the water level rises, the corresponding number appears to indicate the time.

One day and night, totaling 24 hours, is divided into 100 periods, equivalent to 1440 minutes in modern terms. Thus, each period corresponds to 14.4 minutes today.

Tea Time, Incense Time

The term “one tea time” refers to the time it takes to finish a cup of tea, estimated to be about 10 to 15 minutes today; of course, this is not an entirely accurate measure. “One incense time” roughly corresponds to one hour.

• Inventions that helped tell time before clocks
• Explore methods of measuring time
• What does “flipping a seat” mean and what to know about the U.S. midterm elections