Instrument 10 — The Chaldean clock
Every hour has
a ruler.
Long before wristwatches, the day belonged to the planets: twelve unequal hours of daylight, twelve of night, and seven classical planets rotating through them in the ancient Chaldean order. Below, the clock is computed from the true sunrise and sunset of your city — not averaged, not approximated.
Right now in Casablanca The hour of Mercury — until 19:14
● Your city
● Day hours — sunrise to sunset
● Night hours — sunset to sunrise
Computed for Casablanca (33.57°, -7.59°) · times shown in UTC+1 · change city to recompute.
The machinery
A clock made of daylight.
The planetary hours are the oldest scheduled day in the world — older than the zodiac's fixed houses, older than the seven-day week we still keep. The rule is simple and unyielding: the daylight is cut into twelve, the darkness into twelve, and the planets walk their fixed rotation through both. Because the twelfths are of actual daylight, the same hour number has different lengths in June and December — which is why every serious table, including this one, must be computed from the true sunrise and sunset of the observer's city. Ours comes from the ephemeris, the same engine that casts the charts.
The practice
Do the errand under its planet.
The tradition assigns each hour a temperament, and the practice is simply to pair errand with ruler. Sun hours carry visibility — the pitch, the interview, the public ask. Venus hours carry attraction — the reconciliation, the purchase, the portrait. Mercury hours carry language — contracts, emails, study. Moon hours favour home and care; Mars hours, hard physical starts; Jupiter hours, growth and generosity; Saturn hours, the unglamorous discipline of endings and cleanups. None of it is magic and all of it is structure: a day given a rhythm you can plan against.
● More of the live sky
Hours, rulers,
questions.
What are planetary hours?
A timekeeping system older than mechanical clocks: the day (sunrise to sunset) and the night (sunset to the next sunrise) are each divided into twelve hours — unequal by modern clocks, because daylight stretches in summer and shrinks in winter. The seven classical planets then rule those hours in the Chaldean order, so every hour of the week has a presiding planet.
How do I use a planetary hour?
Match the hour's ruler to your errand. Sun hours for visibility and asking for a decision; Venus hours for beauty, money and reconciliation; Mercury hours for writing, trade and paperwork; Moon hours for home and care; Mars hours for hard starts and workouts; Jupiter hours for learning and asking for growth; Saturn hours for discipline, cleaning and ending things. Do the errand under its planet.
Why are the hours unequal?
Because the system predates the clock. An ancient "hour" was simply a twelfth of the daylight — so a summer day-hour ran long and its night-hour ran short, and the ratio flips at the equinoxes. That is why the tables above show actual minutes: each hour is computed from the real sunrise and sunset at your city on today's date.
What is the Chaldean order?
The ancient sequence Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon — the planets ordered by their apparent speed as seen from Earth, slowest to fastest. It runs continuously through every planetary hour, day and night, which is exactly why the first hour of each weekday lands on that day's ruler: Sunday's first hour is the Sun's, Monday's the Moon's, and so on.
Do planetary hours depend on my location?
Yes — completely. The hours are twelfths of real daylight, and daylight depends on latitude and date. Pick your city above and the table recomputes from the ephemeris: Casablanca and Riyadh will show different minute-marks and even different reigning hours on the same day.
Plan the day
by the sky.
The clock above is tonight's; your chart is forever. Cast it once and the hours stop being trivia.