The Chaldean Order: Why Planets Follow This Sequence

The Chaldean order is a short phrase that hides one of the most influential ideas in astrology and chronology: the sequence of seven planets that defined our days of the week, planetary hours, and medieval views on the structure of the cosmos. Let's analyze what it is, where this sequence came from, and why planetary hours don't work without it.

What is the Chaldean order

The Chaldean order is a fixed sequence of the seven classical planets:

Saturn → Jupiter → Mars → Sun → Venus → Mercury → Moon

After the Moon, the order repeats again starting from Saturn. In planetary hours, this chain acts as a sort of "ruler's calendar": each position in the day corresponds to a planet, and every seven hours, the same ruler returns.

At first glance, the order seems strange. Why is the distant, slow Saturn first, rather than the bright Sun or the fast Moon? Why are Venus and Mercury after the Sun, even though they are closer to it in orbit? The answer lies not in the actual structure of the Solar System, but in how the planets appear from Earth.

Order by speed: from the perspective of an Earth observer

In ancient times, all planets were considered celestial bodies rotating around the Earth. With this view, the main characteristic of a planet was not its orbit, but the speed of its apparent motion across the sky relative to the stars.

If you arrange the planets by decreasing speed as they complete a full circle around the zodiac, you get exactly the Chaldean order:

The table shows a pattern: the farther the planet, the slower it moves across the sky. Saturn is the farthest and slowest, the Moon is the closest and fastest. The Chaldean order is simply the order "from farthest to closest" or, what is the same, "from slowest to fastest."

This principle is easy to verify even without instruments: in a single night, the Moon noticeably shifts among the stars, while the position of Saturn or Jupiter between constellations changes so slowly that it can only be noticed over weeks and months of observation.

Why is it called the "Chaldean" order?

The name refers to the Chaldeans, the astronomer-priests of ancient Babylon, who were the first to build a systematic astronomy: they conducted years of observations, calculated the positions of the planets, and divided time into seven. For Greeks and Romans, "Chaldean" was long synonymous with "astrologer," so medieval European authors who found this order in Arabic translations of ancient texts willingly attributed it to the Chaldeans.

Modern science clarifies this picture. The Babylonians indeed provided the foundation: a seven-part division of the sky, observations of the planets, and a lunisolar calendar. However, the complete system of the seven-day week with day rulers, according to historians, took shape in Hellenistic Egypt in the first centuries BC, when Babylonian, Egyptian, and Greek traditions mixed in Alexandria. But the name "Chaldean order" was established in tradition and has reached us as such.

How the Chaldean order creates the days of the week

The most surprising result of the order is the seven-day week. The mechanics are as follows.

The day is divided into 24 hours. The first hour of each day belongs to the planet that rules that day. Then the hours follow the Chaldean order: the second hour is the next planet, and so on in a circle.

Now let's calculate which planet will start the next day. A day has 24 hours. The order consists of 7 planets, which means after 21 hours, we return to the planet of the first hour (24 = 21 + 3, that is, three full cycles of 7 and three more steps). Therefore, the planet of the 25th hour, which is the first hour of the next day, is the planet that is three positions ahead of the current one.

Let's start with Sunday, whose ruler is the Sun. In the Chaldean order, the positions are: Saturn - 1, Jupiter - 2, Mars - 3, Sun - 4, Venus - 5, Mercury - 6, Moon - 7.

• Sunday: Sun (position 4). Next day: 4 + 3 = 7 → Moon.
• Monday: Moon (7). Next day: 7 + 3 = 10, which is 10 - 7 = 3 → Mars.
• Tuesday: Mars (3). Next day: 3 + 3 = 6 → Mercury.
• Wednesday: Mercury (6). Next day: 6 + 3 = 9, 9 - 7 = 2 → Jupiter.
• Thursday: Jupiter (2). Next day: 2 + 3 = 5 → Venus.
• Friday: Venus (5). Next day: 5 + 3 = 8, 8 - 7 = 1 → Saturn.
• Saturday: Saturn (1). Next day: 1 + 3 = 4 → Sun.

This is how the familiar sequence of rulers is born from the Chaldean order:

That is why in English, German, Scandinavian, and Romance languages, the names of the days retained the names of the planets: Sunday - day of the Sun, Monday - day of the Moon, Saturday - day of Saturn, French mardi (day of Mars) and jeudi (day of Jupiter). The shift by three positions per day is the rule that connects the seven-day week with the 24-hour division of the day.

Chaldean order and planetary hours

In planetary hours, the order works in the same way, but within a single day. In the morning, at the moment of sunrise, the first daytime hour goes to the planet of the day of the week. Then every next hour is the next planet in the Chaldean order. After the 12th daytime hour comes the night, and the nightly sequence continues exactly from where the daytime one left off: the 13th hour of the day is again ruled by the next planet in the order.

This gives two important consequences:

• The night chain does not start over. The night does not get "its" separate planet for the first hour; it simply continues a single count of 24 hours.
• Each planet rules for either three or four hours during the day. In 24 hours and seven planets on a circle, the distribution is always almost equal: 24 = 7 × 3 + 3, so three planets get four hours, and four get three.

At night, the first hour is opened by the planet standing after the twelfth position of the daytime count. Therefore, the night ruler (the planet of the first night hour) is different every day and does not coincide with the day ruler, although both obey the same Chaldean order. On lunar.day, the day and night rulers are shown separately on the planetary hours page for each city.

How to manually determine the planet of any hour

The Chaldean order allows you to calculate the ruler of any hour without tables — it is enough to know the ruler of the day. Let's look at an example.

Suppose today is Thursday, and its ruler is Jupiter. We need to find out which planet rules in the third night hour. Let's list the positions in order: Saturn - 1, Jupiter - 2, Mars - 3, Sun - 4, Venus - 5, Mercury - 6, Moon - 7, then the circle repeats.

1. The first daytime hour (hour 1 of the day) is Jupiter, position 2.
2. There are twelve daytime hours, so the 12th hour of the day: 2 + 11 = 13; 13 - 7 = 6 → Mercury.
3. The first night hour is the 13th hour of the day: 6 + 1 = 7 → Moon.
4. The third night hour is the 15th hour of the day: 7 + 2 = 9; 9 - 7 = 2 → Jupiter.

Answer: the third night hour of Thursday is ruled by Jupiter. The same result will be given by the planetary hours table on lunar.day — there is no need to calculate manually, just open the city page and look at the required date.

Such a check is also useful for self-verification: if you have memorized the Chaldean order (Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon), you can restore the planets of all 24 hours of the current day at any moment.

How the seven-day week spread across the world

The connection of the Chaldean order with the week did not remain the property of one culture. In the Vedic astrology of India, the days of the week are named exactly after the same rulers: Ravivar (Sun), Somvar (Moon), Mangalvar (Mars), Budhvar (Mercury), Guruvar (Jupiter), Shukravar (Venus), Shanivar (Saturn). The order is completely identical to the Chaldean one.

The Islamic tradition, which absorbed ancient astronomy through translations into Arabic, preserved the seven-day week, the division of the day into planetary hours, and the Chaldean order itself, although ordinal numbers (first day, second day, etc.) predominate in the Arabic names of the days of the week. Nevertheless, planetary correspondences of the days were preserved in astronomical and magical writings.

From Europe, the week with planetary names spread along with colonization and globalization: English Sunday and Monday, German Sonntag and Montag, Spanish domingo and lunes — all of them refer to the Sun and the Moon as the first rulers of the week.

Interestingly, the Chinese and Japanese calendars also adopted the seven-day week with planetary names, only through the Japanese system of five elements: Sunday - day of the Sun, Monday - day of the Moon, Tuesday - day of Mars (fire), Wednesday - day of Mercury (water), Thursday - day of Jupiter (wood), Friday - day of Venus (gold), Saturday - day of Saturn (earth). And here the Chaldean order remained recognizable.

Chaldean order in cosmology and magic

In the medieval worldview, the Chaldean order was not just for hours. The seven planets were identified with seven celestial spheres, which were located in concentric rings around the Earth — from the sphere of the Moon (the closest) to the sphere of Saturn (the farthest). The order of the spheres "from top to bottom" is the Chaldean: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon.

The same order was the basis for:

• Magic squares and planetary seals — tables of numbers associated with each of the seven planets, which were used in grimoires.
• "Ladder" of seven spheres — the idea of the descent of the soul through the spheres of the planets at birth and the ascent after death, popular in late antique and Mithraic teachings.
• Musical "seven planets - seven notes" — a symbolic parallel between the seven planets and the seven steps of the musical scale.
• Seven metals of alchemy — lead (Saturn), tin (Jupiter), iron (Mars), gold (Sun), copper (Venus), mercury (Mercury), silver (Moon).

All this is a consequence of one principle: the seven planets are the fundamental row of the ancient cosmos, and the Chaldean order is a way to turn this row into a sequence of time.

What each "link" of the order gives

Each of the seven planets in the Chaldean chain carries its own symbolic content, which then passes to the hours and days. Briefly:

• Saturn — border, time, limitation, old, earth. The slowest, the farthest, so it is the most "serious".
• Jupiter — growth, luck, law, knowledge. The second slowest, but the most "beneficent" in the tradition.
• Mars — action, fire, war, energy. Medium speed, hot temper.
• Sun — power, authority, light, masculine principle. The center of the celestial row.
• Venus — love, beauty, union, feminine principle.
• Mercury — word, trade, roads, connection. Fast and changeable.
• Moon — night, growth and waning, home, imagination. The fastest, completes the circle.

This "characteristic" of the planets is directly used in selecting the time for affairs: the hour of Saturn is considered favorable for serious undertakings, the hour of Venus for love and creative affairs, the hour of Mercury for negotiations and study. More details about what to plan in each hour are explained in a separate article.

Common mistakes and clarifications

• Do not confuse with actual distance. The Chaldean order is the order of apparent speed, not the actual distance to the planets. In the heliocentric system, Venus and Mercury are closer to the Sun than Mars, but in the Chaldean order they are after the Sun because they move faster across the sky than it does.
• Do not confuse with zodiacal division into decans. Decans are the division of a zodiac sign into three parts of ten degrees each, and they have their own system of rulers. The Chaldean order concerns only the sequence of planets in time.
• The ruler of the day is not the same as the ruler of the hour. The ruler of the day determines the first daytime hour, but during the day all seven planets rule in turns. For example, on Saturday (day of Saturn), the morning hour is opened by Saturn, but the evening one can belong to Venus or Mercury.
• Three or four hours per planet. It is not always exactly three hours per planet in a day. Because 24 is not evenly divisible by 7, three planets in a day get a fourth hour. This is normal and is embedded in the system itself.
• Do not look for physics in the order. In the heliocentric system, the Sun is in the center, and the order of planets by distance is completely different. The Chaldean order is geocentric and symbolic; its value is not in astronomy, but in tradition and its internal logic.

Why this is important for planetary hours

Without the Chaldean order, planetary hours do not work: the whole system relies on the fact that the sequence of planets is strictly fixed and repeatable. Knowing only two numbers — the ruler of the day of the week and the current hour — you can manually restore any planet of any hour. That is why medieval textbooks could get by with a simple table: "on Sunday in the fifth hour, Mercury rules" — and this is true for any city and any date.

The Chaldean order is not a scientific law, but a tradition. But a surprisingly resilient tradition: it survived Babylon, the Greeks, the Islamic world, the Renaissance, and has lived to the age of digital applications in which we calculate planetary hours by the exact coordinates of sunrise and sunset for any city on Earth.

On the planetary hours page on lunar.day, you will see the Chaldean order in action: the sequence of rulers for 24 hours, the day and night planets, and the current hour. If you want to learn deeper who the Chaldeans were and where this tradition came from, the history of planetary hours will tell you more.