How are the elements of your Zodalys book calculated?
Thank you very much for your interest. This page is currently being expanded and will gradually be completed. Thank you for your patience.
Each Zodalys book is based on precise birth data: date of birth, time of birth, place of birth, first name and birth name. From this information, we calculate different elements drawn from Western astrology, numerology and Chinese Ba Zi astrology.
These calculations follow predefined methods. Some choices are based on astronomical foundations, while others come from symbolic traditions or freer interpretative approaches. As there is more than one way to calculate a birth chart, a numerological profile or a Ba Zi chart, we have chosen to explain here the main methods used in Zodalys books.
The purpose of this page is simple: to bring together, in one place, the main technical and editorial choices on which our calculations are based. The titles below may later lead to more detailed articles.
Western Astrology
How do we calculate the positions of the planets?
Planetary positions are calculated from the date and time of birth. Local time is first converted into Universal Time, providing a common astronomical reference independent of the time zone.
We use Swiss Ephemeris, a recognised astronomical calculation library. The result is a geocentric ecliptic longitude between 0° and 360°. This longitude is then used to determine the zodiac sign: each sign occupies a 30° section of the zodiac.
The celestial bodies included are the Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Although Pluto has been classified as a dwarf planet in astronomy, it remains an important symbolic factor in astrology.
We use the tropical zodiac, which is the most widely used system in Western astrology, rather than the sidereal zodiac, which is more closely associated with Vedic astrology.
House systems: why Placidus and not another one?
Astrological houses divide a birth chart into twelve areas of life. Unlike zodiac signs, they depend on the place of birth, latitude, longitude and exact time of birth.
We use the Placidus house system, one of the most widely used systems in Western astrology. However, other systems also exist, including Koch, Whole Sign, Campanus, Regiomontanus and Equal Houses.
This choice can affect certain results. For example, a planet may fall in the seventh house using Placidus but in the eighth house using another system. This is one reason why two programs can sometimes produce different results.
Placidus also has its limits, particularly at extreme latitudes. For births in the most common European and American latitudes, however, it remains a widely used and meaningful compromise.
The Ascendant and the Midheaven: two central pillars of the birth chart
The Ascendant is the point of the ecliptic rising on the eastern horizon at the exact moment of birth. It therefore depends strongly on the time, place, latitude and longitude of birth.
The Midheaven, also called the MC or Medium Coeli, corresponds to the highest point of the chart at the meridian of the birthplace. In the Placidus system, the Ascendant marks the beginning of the first house, while the Midheaven marks the beginning of the tenth house.
These points move quickly. A difference of only a few minutes in the recorded birth time can shift the Ascendant by around one degree, or even move it into the following sign when it is close to a sign boundary.
The Descendant and the Imum Coeli are calculated through geometric opposition: the Descendant lies opposite the Ascendant, while the Imum Coeli lies opposite the Midheaven.
The North Node: Mean or True?
The lunar nodes are the two points where the Moon’s orbit intersects the ecliptic. They are therefore not planets, but calculated astronomical points.
We use the Mean North Node. This is a mathematically smoothed position with regular retrograde motion and a cycle of approximately 18.6 years.
There is also the True North Node, sometimes called the Oscillating Node. It reflects a more immediate position and can move slightly around the Mean Node.
In practice, the difference can reach approximately 1.5°. This may be enough to place the North Node in a different sign when it lies very close to a sign boundary.
Lilith: which one exactly?
The name Lilith can refer to several different points in astrology. This is why two programs may sometimes display significantly different results for the same birth data.
In our calculations, we mainly use Mean Lilith. It corresponds to the mean apogee of the Moon’s orbit and is one of the most commonly used versions in French-speaking astrology.
There is also True or Oscillating Lilith, which follows the instantaneous position of the lunar apogee. It can differ from Mean Lilith by several degrees.
In some cases, this difference may be large enough to place Lilith in another sign. This does not necessarily indicate an error, but rather a difference in calculation method.
The Part of Fortune: the day and night formula
The Part of Fortune is a fictional point inherited from ancient astrology. It is not a real planet, but a point calculated from the Ascendant, the Sun and the Moon.
We use the traditional distinction between day charts and night charts. If the Sun is above the horizon, the formula is: Ascendant + Moon − Sun.
If the Sun is below the horizon, the formula becomes: Ascendant + Sun − Moon.
Some modern schools use the same formula regardless of the time of birth. We have chosen to preserve the distinction between day and night charts, in keeping with astrological tradition.
Modern or traditional rulerships: our choice
In astrology, each sign is associated with a ruling planet. Traditional rulerships use the seven celestial bodies visible to the naked eye: the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn.
Modern rulerships include Uranus, Neptune and Pluto, which were discovered later. In this system, Uranus is associated with Aquarius, Neptune with Pisces and Pluto with Scorpio.
In Zodalys books, we use modern rulerships. This choice influences certain calculations, particularly those relating to planetary dominance and house rulers.
A traditional astrologer may therefore assign different rulers to some signs. Here again, this is a matter of school and method rather than a simple opposition between right and wrong.
The dominant planet: how we calculate this score
The dominant planet is not a purely astronomical piece of information. It is an interpretative score calculated from several criteria.
Our method takes into account, among other factors, a planet’s house position, its proximity to the angles of the chart, certain astrological dignities, received aspects and possible retrograde motion.
For example, a planet placed in an angular house or close to the Ascendant, Midheaven, Descendant or Imum Coeli receives greater weight.
This scoring system is specific to Zodalys. It does not exactly reproduce the methods used by other programs or astrological schools, but it is based on a consistent weighting applied throughout all our books.
Numerology
The Pythagorean table: how letters become numbers
The numerology used in Zodalys books is mainly based on the Pythagorean system. In this system, letters are assigned numbers from 1 to 9.
The principle is simple: A corresponds to 1, B to 2, C to 3, and so on until I, which corresponds to 9. The cycle then begins again: J corresponds to 1, K to 2, L to 3, and so forth.
Before the calculation, accents are simplified: É becomes E, Ç becomes C and Ñ becomes N. This allows first names and surnames from different European languages to be processed more consistently.
At Zodalys, Y is treated as a vowel for the calculation of the Soul Urge Number. Some schools treat it differently, which can affect certain results.
Master Numbers 11, 22 and 33 are preserved in the relevant calculations instead of being automatically reduced further.
The 8 numbers of your numerological profile
A numerological profile is not limited to the Life Path Number. In Zodalys books, several numbers are calculated to offer a broader interpretation.
The Life Path Number is calculated from the date of birth. It is obtained by adding together the digits of the day, month and year, then reducing the result.
The Expression Number is calculated from all the letters in the first names and birth names. The Soul Urge Number is based on vowels, while the Personality Number is based on consonants.
The Active Number uses the first commonly used first name. The Hereditary Number is based on the family name or names. The Maturity Number combines the Expression Number and the Life Path Number.
The Birthday Number, sometimes called the Birth Force Number, is derived from the day of birth. The numbers 11 and 22 may be preserved, while 33 is not possible because a birthday cannot exceed 31.
The Pythagorean Square: the number grid of your birth date
The Pythagorean Square is built from the digits contained in the birth date. The digits from the day, month and year are extracted, then the number of occurrences of each digit from 1 to 9 is counted.
Zero is not included. According to certain schools, missing numbers can be interpreted as areas of development or energies that may be less naturally available.
Numbers that appear several times indicate more strongly emphasised energies. A number that appears two or three times therefore does not carry the same weight as a number that appears only once.
This method is particularly well known in certain numerological traditions from Eastern Europe, although it is less widespread in France than the traditional Life Path approach.
Chinese Ba Zi Astrology
The Four Pillars: how is your Ba Zi calculated?
Ba Zi, also known as the Four Pillars, is based on the date and time of birth. It consists of four pillars: Year, Month, Day and Hour.
Each pillar combines a Heavenly Stem and an Earthly Branch. The Heavenly Stems combine an element with a Yin or Yang polarity. The Earthly Branches are notably associated with the twelve animals of the Chinese zodiac.
The Ba Zi year does not necessarily begin on 1 January. It changes around 4 February with Li Chun, the beginning of the Chinese solar spring. A person born in January may therefore still belong to the previous Ba Zi year.
The Month Pillar is based on the Chinese Solar Terms, which divide the year according to precise astronomical markers. The Hour Pillar divides the day into twelve periods of two hours each.
For the Hour Pillar, we use local solar time rather than civil time alone, as geographical longitude can slightly affect the correspondence with the relevant hour branch.
The Hidden Heavenly Stems: the invisible layer of Ba Zi
In Ba Zi, each Earthly Branch can contain one or several Hidden Heavenly Stems. This invisible layer brings additional nuance to the analysis of a chart.
For example, the Tiger Branch contains several internal energies, while the Rat Branch is more concentrated. These hidden contents come from Ba Zi tradition.
In our calculations, Hidden Heavenly Stems contribute in particular to the assessment of the five elements. Their weight depends both on their importance within the Earthly Branch and on the position of the relevant pillar.
There are slight variations between schools and Ba Zi masters. The values used by Zodalys follow a coherent logic applied consistently to every chart.
The 10 Gods: the relational compass of Ba Zi
The 10 Gods, also called Shi Shen, describe the relationships between the Day Master and the other energies of a chart. The Day Master is the Heavenly Stem of the Day Pillar and forms the central point of reference in the chart.
Each other stem is analysed in relation to this Day Master: whether it belongs to the same element or a different one, whether it has the same or opposite polarity, and whether it produces, controls or is controlled.
These relationships create ten symbolic categories, including Friend, Rob Wealth, Eating God, Direct Officer, Seven Killings and Resources.
This method is one of the classic foundations of Ba Zi. It allows for a more detailed reading of personal, relational, professional and behavioural dynamics.
The proportion of elements in your Ba Zi chart
The proportion of the five elements describes the distribution of Wood, Fire, Earth, Metal and Water in a Ba Zi chart.
At Zodalys, the calculation begins with the four visible Heavenly Stems, then incorporates the Hidden Heavenly Stems contained in the Earthly Branches. Each position receives a different weight depending on the pillar involved.
The month of birth then plays an important role because it indicates the season. In Ba Zi, an element does not have the same strength in summer, winter, spring or autumn.
We also take roots into account, meaning the support a Heavenly Stem may find in the Earthly Branches of the chart.
The final result is normalised to obtain a percentage distribution. Certain complex Ba Zi transformations are not yet included, but the method covers the essential part of the chart’s energetic structure.
The Yin/Yang proportion in your Ba Zi chart
The calculation of Yin and Yang follows a similar logic to the calculation of the five elements, with one important difference: seasonal coefficients are not applied.
A season can strengthen an element, but it does not automatically make the entire chart more Yin or more Yang. This is why this proportion is treated separately.
Each visible or hidden Heavenly Stem has a Yin or Yang polarity. The Earthly Branches themselves are not counted independently as Yin or Yang, but are considered through their Hidden Heavenly Stems.
The result makes it possible to observe a general tendency, such as a Yin or Yang predominance, which can then be interpreted within the overall context of the chart.
Understanding differences between programs
Why can two astrology programs give different results?
Two programs can display different results without there necessarily being an error. In most cases, these differences arise from different methodological choices.
In Western astrology, variations may come from the house system used, the choice between the Mean and True North Node, the Lilith selected, the Part of Fortune formula, planetary rulerships, or the tropical versus sidereal zodiac.
In numerology, differences may arise from the treatment of Y, the preservation of Master Numbers, or the method used to reduce the Life Path Number.
In Ba Zi, differences may come from the Jia Zi reference date used, the ratios attributed to Hidden Heavenly Stems, the use of local solar time, or the inclusion of certain advanced transformations.
At Zodalys, we have chosen to document the main conventions we use so that every reader can understand the logic behind their book. Our aim is not to claim that only one method holds the entire truth, but to apply clear, stable and coherent choices.
Summary
The calculations used in a Zodalys book are based on precise conventions. Some are astronomical in nature, while others come from symbolic traditions or deliberate interpretative choices.
This transparency helps you better understand how a personalised portrait is built, and why some results may occasionally differ slightly from those shown on another website or program.
This page may later be expanded with more detailed articles, but it already presents the main methods used to create Zodalys books.
