This table shows how the names of the days, derived from the same Latin astrological background, evolved differently across language families.
| Governing star | Latin origin | French (Romance language) | Spanish (Romance language) | English (Germanic language) | Etymology |
|---|---|---|---|---|---|
| ☉ Sun | Dies Solis | Dimanche | Domingo | Sunday | From Latin dominicus (Lord's day). English retains the solar reference. |
| ☾ Moon | Dies Lunae | Lundi | Lunes | Monday | Directly derived from the Latin name for the Moon (Luna). |
| ♂ Mars | Dies Martis | Mardi | Martes | Tuesday | From the Roman god Mars. English comes from Tiw (Germanic god of war). |
| ☿ Mercury | Dies Mercurii | Mercredi | Miércoles | Wednesday | From the Roman god Mercury. English comes from Woden (Odin, supreme Germanic god). |
| ♃ Jupiter | Dies Jovis | Jeudi | Jueves | Thursday | From the Roman god Jupiter/Jove. English comes from Thor, its Nordic equivalent. |
| ♀ Venus | Dies Veneris | Vendredi | Viernes | Friday | From the Roman goddess Venus. English comes from Frigg or Freya, Nordic goddesses of love. |
| ♄ Saturn | Dies Saturni | Samedi | Sábado | Saturday | French and Spanish derive from the Hebrew Sabbat. English retains the reference to Saturn. |
The key to this order lies in the observation of the ancient sky. Mesopotamian, then Greek and Roman civilizations identified seven "wandering stars" visible to the naked eye, which they called "planets": the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn. According to the geocentric cosmology of the time, it was believed that these celestial bodies exerted an influence on human affairs.
The established order of our days (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday) is so familiar to us that it seems natural. Yet, this succession is not the result of chance, but the product of a learned tradition over two millennia old, blending Babylonian astronomy, Roman mythology, and astrological calculations.
The so-called "Chaldean" order of the planets (Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon) was established by Babylonian astronomers between the 8th and 6th centuries BCE. It was determined by the apparent orbital periods around the Earth, from longest to shortest, according to the geocentric model of the time. This order of "presumed slowness" classified the planets as follows: Saturn (≈ 29.5 years, the slowest), Jupiter (≈ 11.9 years), Mars (≈ 687 days), Sun (≈ 1 year), Venus (≈ 224 days), Mercury (≈ 88 days), Moon (≈ 27.3 days, the fastest).
This order was then adopted by the Greeks, then systematized by Roman scholars such as Ptolemy (2nd century CE) for astrology and the calculation of planetary hours.
Each hour of the day and night was governed by a planet in a perpetual cycle, influencing, according to beliefs, the auspicious moment to undertake any action.
This attribution followed a precise cycle based on the supposed order of the planets. The first hour was governed by Saturn (the slowest planet), then a cyclical sequence was applied.
Saturn ruled the first hour of the day. The 8th, 15th, and 22nd hours also returned to Saturn. In order of "slowness", the 23rd hour was governed by Jupiter, and the 24th hour was governed by Mars. The first hour of the following day therefore returned to the Sun.
By continuing this logic, we obtained the order of the days as we know them. The entire day took the name of the planet that governed its first hour. Thus was born the sequence: Saturn (Saturday), Sun (Sunday), Moon (Monday), Mars (Tuesday), Mercury (Wednesday), Jupiter (Thursday), Venus (Friday).
If we start the cycle with Saturn (1st hour of the 1st day), then by applying the 24-hour rule, we obtain the ancient/original order of the days as used in Roman times.
| Day Latin name | 1st hour → "Master of the day" | Following hours (cyclical sequence) | 24th hour (last) |
|---|---|---|---|
| Saturday Dies Saturni | ♄ Saturn | ♃ → ♂ → ☉ → ♀ → ☿ → ☾ → ♄ → ... | ♂ Mars |
| Sunday Dies Solis | ☉ Sun (next in order after Mars) | ♀ → ☿ → ☾ → ♄ → ♃ → ♂ → ☉ → ... | ☿ Mercury |
| Monday Dies Lunae | ☾ Moon (next after Mercury) | ♄ → ♃ → ♂ → ☉ → ♀ → ☿ → ☾ → ... | ♀ Venus |
| Tuesday Dies Martis | ♂ Mars (next after Venus) | ☉ → ♀ → ☿ → ☾ → ♄ → ♃ → ♂ → ... | ♃ Jupiter |
| Wednesday Dies Mercurii | ☿ Mercury (next after Jupiter) | ♀ → ☾ → ♄ → ♃ → ♂ → ☉ → ☿ → ... | ☾ Moon |
| Thursday Dies Jovis | ♃ Jupiter (next after Moon) | ♂ → ☉ → ♀ → ☿ → ☾ → ♄ → ♃ → ... | ♄ Saturn |
| Friday Dies Veneris | ♀ Venus (next after Saturn) | ☿ → ☾ → ♄ → ♃ → ♂ → ☉ → ♀ → ... | ☉ Sun |
Note: The sequence of planets in the cycle is always the same: ♄ Saturn → ♃ Jupiter → ♂ Mars → ☉ Sun → ♀ Venus → ☿ Mercury → ☾ Moon → (then it starts again). The apparent "jump" between the master of one day and that of the next is due to the 24 intervening hours.
There is no natural first day of the week. The placement of Sunday or Monday at the head of the weekly cycle is a matter of cultural and religious conventions. Sunday long held this position in the West due to its importance in biblical and Christian tradition, institutionalized in the time of Constantine. Conversely, the ISO 8601 standard, adopted in 1988, sets Monday as the first day of the week in a secular and administrative context.
| First day | Last day (weekend) | Global coverage | Basis |
|---|---|---|---|
| Monday | Sunday | ~65% of the world population (Europe, Asia, Africa, South America) | ISO Standard (organizational logic) |
| Sunday | Saturday | ~30% of the world population (North America, Australia, Israel, Philippines) | Religious tradition (Judeo-Christian heritage) |
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