The Twelve Earthly Branches: Animals, Hours and Months

The twelve earthly branches are the lower half of every pillar. The same twelve signs name the years of the zodiac animals, divide the day into two-hour periods and mark the months, which makes them the calendar's all-purpose clock.

What the branches are

The earthly branches (地支, Korean 지지) are twelve signs in a fixed order: 子 丑 寅 卯 辰 巳 午 未 申 酉 戌 亥. Where the ten stems count in tens, the branches count in twelves, a number that fits the twelve months of the year. Most people know them through the zodiac animals, the Rat, Ox, Tiger and so on, which the tradition attaches to the branches as friendly names that are easy to remember.

In a Four Pillars chart each pillar has a branch under its stem. The tradition reads the branch as the ground the stem stands on: the season, the setting and the time. A branch is also richer than a stem, because it carries one to three hidden stems inside it.

The twelve branches at a glance

The table lists every branch with its animal, element, season, two-hour period on the clock and the lunar month it stands for, exactly as the haru engine stores them.

The branches as a clock

Twelve branches share out twenty-four hours, so each one covers a double hour of two hours. The count starts with 子 across midnight, from 23:00 to 01:00, and reaches 午 at midday, from 11:00 to 13:00. That is where the Korean word for noon, 정오 (正午), comes from: it literally means the true 午 hour.

For a chart, the haru engine does not read these hours straight off the wall clock. It first converts the birth time to true solar time for the birthplace, because the sun, not the time zone, decides which double hour it is. The true-solar-time and hour-pillar pages explain how.

The branches as a calendar

The branches also name the months. The first lunar month belongs to 寅, the Tiger, and the months run on from there, so 子 lands on month 11, the month that holds the winter solstice. The seasons follow in groups of three: 寅 卯 辰 for spring, 巳 午 未 for summer, 申 酉 戌 for autumn and 亥 子 丑 for winter.

Look at the element column and a pattern appears. The first two branches of each season carry the season's own element, Wood for spring, Fire for summer, Metal for autumn and Water for winter, while the last branch of every season, 辰, 未, 戌 and 丑, is Earth. The tradition reads these four as the turning points where one season hands over to the next. For the month pillar itself, the months are counted from the solar terms rather than from the new moon; the month-pillar page covers that.

Finding the animal of a year

Branches repeat every twelve years, so the year's animal can be found with the same kind of rule as the stems: subtract 4 and take the remainder after dividing by 12. For 2026: 2026 minus 4 is 2022, and 2022 mod 12 is 6. Counting from 子 as 0, position 6 is 午, the Horse, and the facts file confirms that 2026 is a 丙午 year. Twelve years on, 2038 is 戊午, another Horse, while 2032 brings the Rat again as 壬子.

As with the stems, the pillar year changes at Start of Spring in early February, not on 1 January, so someone born in mid-January 2026 still counts as a Snake (乙巳) in the Four Pillars system.

Yin and yang among the branches

Branches alternate yang and yin just like the stems, six of each. The engine counts 子 as yang and then alternates, so the Rat, Tiger, Dragon, Horse, Monkey and Dog are yang, and the Ox, Rabbit, Snake, Goat, Rooster and Pig are yin. Branches that sit six places apart on the circle, such as 子 and 午, face each other directly; that relationship is the subject of the page on clashes.

Questions

Why does the Rat hour start at 23:00 and not at midnight?

Each double hour begins on an odd hour and is centred on an even one. The 子 hour is centred on midnight, so it runs from 23:00 to 01:00, and the 午 hour is centred on noon.

Is my zodiac animal the same as my year branch?

Yes, the animal is simply the friendly name of the year branch, as long as the year is counted from Start of Spring in early February.

Why is lunar month 1 the Tiger and not the Rat?

The branches are fixed to the seasons: 子 marks the month of the winter solstice, month 11, and counting on from there puts 寅 at the start of spring in month 1.

Do animals describe personality?

Popular culture often uses them that way. In the Four Pillars tradition, the year branch is only one of eight characters and is read together with the others.

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Traditional Four Pillars (myeongni) and yin-yang five-element interpretation. Not a medical diagnosis or advice.