Planetary hours are a timing technique that works from the Sun rather than the clock. Sunrise to sunset is divided into twelve equal parts, sunset to the next sunrise into twelve more, and each part is assigned to one of the seven classical planets. Because the assignment follows a fixed sequence, knowing the ruler of the first hour is enough to reconstruct the cycle.
Three rules govern the method, and almost every serious error comes from breaking one of them. A planetary hour is not sixty minutes. A planetary day does not begin at midnight. The sequence of rulers does not restart at sunset.
The method answers two questions: which planet governs a given interval, and which day and hour best match an intended action. The first belongs to the analysis of time, the second to electional astrology. The arithmetic is the same, but election also requires an assessment of the planet's condition in the chart.
Planetary hours do not replace a full chart. They will not cancel a retrograde significator, repair a void-of-course Moon, or guarantee an outcome. They add a layer that shows whether a moment fits the nature of the matter. A sound election begins with the chart, continues with the Moon and the significators, and only then is refined by the day and the hour.
> In brief. Daylight is divided into twelve equal parts and darkness into twelve more. The first day hour belongs to the ruler of the day, and the planets then follow the Chaldean order without a break at sunset. The twenty-four hours end at the next sunrise, where a new planetary day begins.
1. Five terms that are often confused
| Term | Meaning | Boundaries |
|---|---|---|
| Planetary day | A solar cycle governed by one planet | From sunrise on the chosen date to the next sunrise |
| Day hour | One twelfth of the daylight interval | Sunrise to sunset |
| Night hour | One twelfth of the darkness interval | Sunset to the next sunrise |
| Planetary week | A continuous seven-day cycle with fixed rulers | Seven planetary days |
| Ruler of the hour | The planet assigned to a specific interval | Determined by sequence, not by the clock |
Planetary hours are tied to the real horizon, not to a time zone. Two cities in the same zone can have different sunrise and sunset times, and therefore different hour boundaries. Civil time is useful for schedules, but it does not describe where the Sun stands relative to a particular place.
Several conventions exist for the start of the planetary day. The sunrise convention is the most widespread and is used here; sunset and midnight conventions also appear. Whatever convention is chosen must be applied consistently, or the day ruler and the table of hours will contradict each other.
2. The planetary week
The seven days of the week are traditionally linked to the seven planets visible to the naked eye. Each day has a ruler, and that ruler also governs the first hour after sunrise.
| Day | Ruler | Traditional theme |
|---|---|---|
| Monday | Moon | Receptivity, home, family, public contact, change |
| Tuesday | Mars | Action, competition, tools, speed, defence |
| Wednesday | Mercury | Information, documents, trade, learning, short journeys |
| Thursday | Jupiter | Expansion, law, education, patronage, large plans |
| Friday | Venus | Relationships, beauty, art, agreement, pleasure |
| Saturday | Saturn | Structure, limits, completion, land, long obligations |
| Sunday | Sun | Authority, recognition, visibility, vitality |
The ruler of the day sets the background, while the ruler of the hour supplies a narrower tone. This is a hierarchy rather than two equal layers. The day answers the question of what theme colours the period as a whole; the hour shows what is amplified in a particular interval. When the two rulers coincide, the theme of the day is more pronounced. When the hour belongs to a planet of opposite character, the result may be mixed.
3. The Chaldean order
The Chaldean order arranges the seven classical planets from slowest to fastest. In the traditional model it corresponds to the order of the spheres: the farther a planet, the slower its motion through the zodiac.
| Position | Planet | Orbital period | Mean zodiac motion | Day |
|---|---|---|---|---|
| 1 | Saturn | about 29.5 years | about 0.03° per day | Saturday |
| 2 | Jupiter | about 11.9 years | about 0.08° per day | Thursday |
| 3 | Mars | about 1.9 years | about 0.52° per day | Tuesday |
| 4 | Sun | about 1 year | about 0.99° per day | Sunday |
| 5 | Venus | about 225 days | about 1.2° per day | Friday |
| 6 | Mercury | about 88 days | about 1.4° per day | Wednesday |
| 7 | Moon | about 27.3 days | about 13.2° per day | Monday |
The sequence is closed: after the Moon comes Saturn again, which allows the hours to continue indefinitely without resetting at a day boundary. Within the hours the step is always one place.
3.1. Why the order of days differs from the order of hours
The Chaldean order and the order of the weekdays are different sequences, although the second is derived from the first. Give the first hour of a day to Saturn. After twenty-four hours the sequence has advanced twenty-four steps; twenty-four modulo seven is three. The first hour of the next day therefore goes to the planet three places after Saturn, the Sun. The next shift gives the Moon, then Mars, Mercury, Jupiter, Venus, and Saturn again.
This is not a contradiction: the Chaldean order describes the succession within a day, while the order of days is the result of a twenty-four-hour step, a shift of three places.
4. Why the hours are unequal
The historical name for planetary hours is "unequal hours" or "seasonal hours." They are not unequal to each other within the same half of the day; they are unequal to the civil hour and to the hours of the other half. In summer the day hour is longer than the night hour; in winter it is shorter.
day_length = sunset − sunrise
night_length = 1440 − sunset + next_sunrise
day_hour = day_length / 12
night_hour = night_length / 12
Measured in minutes after local midnight, the night length is 1440 − sunset + next_sunrise. This form automatically handles the passage through midnight. The length of an hour depends on latitude and season: the farther a place is from the equator, the more the balance of day and night changes across the year.
| Latitude | June solstice | December solstice | Equinox |
|---|---|---|---|
| 0° | about 61 | about 61 | about 61 |
| 40° | about 75 | about 47 | about 61 |
| 50° | about 82 | about 40 | about 61 |
| 55.8° | about 88 | about 35 | about 61 |
| 60° | about 94 | about 29 | about 61 |
| 66.5° | polar day | about 11 | about 61 |
The values are rounded and calculated for sea level with standard refraction; they indicate orders of magnitude, not an exact timetable.
At the equinox, daylight is slightly longer than twelve hours because of refraction and the finite size of the solar disc, so "exactly sixty minutes" is an approximation. Above the polar circle the Sun may not rise or set for weeks, and the formula becomes undefined. Conventions include equal intervals, a nearest-latitude proxy, an anchor at upper culmination, civil twilight, or suspending the hour division; the convention must be stated explicitly.
5. Calculation for a date and place
The calculation needs the coordinates, the local date, the time zone in force, and three moments: sunrise, sunset, and the next sunrise. Coordinates to a tenth of a degree are enough for most cities; large conurbations can differ by a minute or two at the boundaries. For an online event, choose the place of the person initiating the action and keep that rule fixed. The third moment is essential; without it the night cannot be measured.
Convert the times to minutes after midnight. For example, 04:24 is 264 minutes, 20:27 is 1227 minutes, and a next sunrise at 04:22 is 262 minutes on the following day. Then:
day_length = sunset − sunrise
night_length = 1440 − sunset + next_sunrise
day_hour = day_length / 12
night_hour = night_length / 12
Check that twelve day hours add up to the day length and twelve night hours to the night length. The twenty-four hours together are close to 1440 minutes but need not equal it exactly, because sunrise shifts from day to day.
The planetary day begins at sunrise, so time after midnight but before sunrise belongs to the previous day. The first day hour belongs to the ruler of the day. The sequence is:
Saturn → Jupiter → Mars → Sun → Venus → Mercury → Moon → Saturn
ruler(k) = order[(day_index + k − 1) mod 7]
start(k) = sunrise + (k − 1) × day_hour, k = 1…12
start(k) = sunset + (k − 13) × night_hour, k = 13…24
Treat boundaries as half-open intervals: the starting moment belongs to the new hour, the ending moment to the following one. To locate a moment, use k = floor((time − sunrise) / day_hour) + 1 during the day and the analogous formula at night through the night offset.
Useful checks: the day ruler recurs in hours 1, 8, 15, and 22; hour 13 begins at sunset; hour 24 ends at the next sunrise; the next day's first hour is three places further along; and the day ruler plus the next two planets receive four hours each, the other four receive three.
6. Worked example: New York, Thursday 14 January 2027
Inputs: 40.71° north, 74.01° west; time zone UTC−5, standard time; sunrise 07:18; sunset 16:51; next sunrise on 15 January at 07:18; weekday Thursday, ruled by Jupiter.
Calculation: day length 16:51 − 07:18 = 9 hours 33 minutes = 573 minutes; day hour 573 / 12 = 47.75 minutes, or 47 minutes 45 seconds. Night length 1440 − 1011 + 438 = 867 minutes, or 14 hours 27 minutes; night hour 867 / 12 = 72.25 minutes, or 72 minutes 15 seconds.
| No. | Ruler | Start | End |
|---|---|---|---|
| 1 | Jupiter | 07:18 | 08:06 |
| 2 | Mars | 08:06 | 08:54 |
| 3 | Sun | 08:54 | 09:41 |
| 4 | Venus | 09:41 | 10:29 |
| 5 | Mercury | 10:29 | 11:17 |
| 6 | Moon | 11:17 | 12:04 |
| 7 | Saturn | 12:04 | 12:52 |
| 8 | Jupiter | 12:52 | 13:40 |
| 9 | Mars | 13:40 | 14:28 |
| 10 | Sun | 14:28 | 15:16 |
| 11 | Venus | 15:16 | 16:03 |
| 12 | Mercury | 16:03 | 16:51 |
| 13 | Moon | 16:51 | 18:03 |
| 14 | Saturn | 18:03 | 19:16 |
| 15 | Jupiter | 19:16 | 20:28 |
| 16 | Mars | 20:28 | 21:40 |
| 17 | Sun | 21:40 | 22:52 |
| 18 | Venus | 22:52 | 00:04 |
| 19 | Mercury | 00:04 | 01:17 |
| 20 | Moon | 01:17 | 02:29 |
| 21 | Saturn | 02:29 | 03:41 |
| 22 | Jupiter | 03:41 | 04:54 |
| 23 | Mars | 04:54 | 06:06 |
| 24 | Sun | 06:06 | 07:18 |
Queries:
- 10:00. 162 minutes after sunrise. 162 / 47.75 = 3.39, so this is the fourth hour, Venus, 09:41–10:29.
Note that 02:00 on Friday by the civil calendar is still planetary Thursday, because the new day does not begin until 07:18. In the table, 02:00 falls in the twenty-first hour, Saturn.
7. Worked example: Singapore, Monday 8 February 2027
The second example provides a contrast: near the equator day and night are almost equal, so planetary hours are close to ordinary hours.
Inputs: 1.35° north, 103.82° east; time zone UTC+8; sunrise 07:17; sunset 19:21; next sunrise on 9 February at 07:17; weekday Monday, ruled by the Moon.
Calculation: day length 19:21 − 07:17 = 12 hours 04 minutes = 724 minutes; day hour 724 / 12 = 60.33 minutes, or 60 minutes 20 seconds. Night length 1440 − 1161 + 437 = 716 minutes, or 11 hours 56 minutes; night hour 716 / 12 = 59.67 minutes, or 59 minutes 40 seconds.
| No. | Ruler | Start | End |
|---|---|---|---|
| 1 | Moon | 07:17 | 08:17 |
| 2 | Saturn | 08:17 | 09:18 |
| 3 | Jupiter | 09:18 | 10:18 |
| 4 | Mars | 10:18 | 11:18 |
| 5 | Sun | 11:18 | 12:19 |
| 6 | Venus | 12:19 | 13:19 |
| 7 | Mercury | 13:19 | 14:19 |
| 8 | Moon | 14:19 | 15:20 |
| 9 | Saturn | 15:20 | 16:20 |
| 10 | Jupiter | 16:20 | 17:20 |
| 11 | Mars | 17:20 | 18:21 |
| 12 | Sun | 18:21 | 19:21 |
| 13 | Venus | 19:21 | 20:21 |
| 14 | Mercury | 20:21 | 21:20 |
| 15 | Moon | 21:20 | 22:20 |
| 16 | Saturn | 22:20 | 23:20 |
| 17 | Jupiter | 23:20 | 00:19 |
| 18 | Mars | 00:19 | 01:19 |
| 19 | Sun | 01:19 | 02:19 |
| 20 | Venus | 02:19 | 03:18 |
| 21 | Mercury | 03:18 | 04:18 |
| 22 | Moon | 04:18 | 05:18 |
| 23 | Saturn | 05:18 | 06:17 |
| 24 | Jupiter | 06:17 | 07:17 |
Queries:
- 09:00. 103 minutes after sunrise. 103 / 60.33 = 1.71, so this is the second hour, Saturn, 08:17–09:18.
The contrast is instructive. In New York in winter the day hour is about 48 minutes and the night hour about 72, a ratio of roughly 1.5. In Singapore the two differ by less than a minute. "A planetary hour" without a place and a date therefore means little: it may be forty-eight minutes, seventy-two minutes, or a hundred and ten.
8. Reading the ruler of the hour
The interpretation of an hour rests on the traditional nature of the planet. This is symbolic language, not a physical force: the planet sets a theme and a mode of action but does not guarantee an event. The condition of the planet in the chart matters more than its name. Saturn in fall does not become favourable because its hour has arrived.
| Planet | Character of the hour | Suitable | Avoid |
|---|---|---|---|
| Saturn | Contraction, structure, patience | Planning, documents, repairs, land, completions | Celebrations, risky finance, light social contact |
| Jupiter | Expansion, law, patronage | Courts, study, publication, long journeys, large agreements | Petty routine, extreme thrift |
| Mars | Action, speed, competition | Sport, repairs, urgent tasks, defending boundaries | Delicate talks, weddings, reconciliation |
| Sun | Visibility, authority, recognition | Presentations, official requests, creative launches | Secret deals, backstage intrigue |
| Venus | Agreement, beauty, relationship | Dates, engagements, diplomacy, art, gifts | Hard bargaining, competition |
| Mercury | Information, documents, learning | Correspondence, exams, trade, short trips | Long commitments with an afflicted Mercury |
| Moon | Receptivity, change, home | Domestic matters, care, gathering information, water | Decisions that require firmness |
The table is a starting point, not a substitute for the chart. Mars in a Saturn hour may produce restrained action, and Venus in a Mars hour may produce persistence. Day and hour combine as a matrix: coincidence makes the theme louder, related planets make it gentler, opposite planets mix it. Perfect coincidence is not required; the day must not contradict the matter, and the hour must not undermine it.
9. Electional use
Planetary hours are a secondary filter for an electional chart, not a replacement for it. A full election considers the ascendant of the moment, the Moon, the ruler of the house of the matter, the aspects between significators, and whether the main indicator is damaged. The hours add one layer: whether the moment matches the nature of the work.
A sensible hierarchy is:
1. The chart of the moment. If the Moon is void of course, the significator is destroyed, or the house of the matter is afflicted, a good hour will not save the election.
2. The condition of the Moon. Its sign, aspects, and phase matter more than the choice of hour.
3. The ruler of the day. It sets the general tone and should not contradict the matter.
4. The ruler of the hour. It should match the matter or support its significator.
5. The condition of the hour ruler. Retrograde motion, combustion, fall, and exile weaken a planet. The hour of a "strong" planet in poor condition is not a good hour.
6. The moment of beginning. Start at the beginning of the hour; an action begun before the boundary belongs to the previous hour.
| Matter | Natural significator | Preferred day | Preferred hour |
|---|---|---|---|
| Contract, negotiation, documents | Mercury | Wednesday | Mercury |
| Interview, request to authority | Sun | Sunday | Sun or Mercury |
| Court, education, publication, long journey | Jupiter | Thursday | Jupiter |
| Marriage, engagement, reconciliation, beauty | Venus | Friday | Venus |
| Sport, competition, repairs | Mars | Tuesday | Mars |
| Long obligations, land, completions | Saturn | Saturday | Saturn |
| Home, family, public, water, short changes | Moon | Monday | Moon |
The table is a starting point. If the significator in the chart is not the planet listed, the chart has priority: with an afflicted Venus and a strong Jupiter ruling the seventh house, rely on Jupiter rather than taking Venus mechanically.
Planetary hours do not compensate for a poor chart or guarantee an outcome; they fine-tune a moment that is already good or acceptable.
10. Limits and common mistakes
In horary and natal practice the hour ruler is an additional testimony, not proof. It is weaker than the ascendant, the Sun, the Moon, and the significators, and it does not replace the chart.
Daylight saving time, time zones, and high latitudes. On a changeover day, convert all times to UTC, do the arithmetic, and convert back. Near the polar circle an average day length for the week is not acceptable, and during polar day or night the convention must be stated.
1. Treating a planetary hour as sixty minutes. That is true only near the equator and near the equinox. In middle latitudes a summer day hour can last an hour and a half, while a winter day hour can be about forty minutes.
2. Dividing the civil day into twenty-four equal parts. Planetary hours divide daylight and darkness separately.
3. Starting the planetary day at midnight. The day begins at sunrise; time from 00:00 to sunrise belongs to the previous day.
4. Resetting the Chaldean order at sunset. The sequence is continuous: hour 13 continues it rather than starting again from the day ruler.
5. Mixing UTC and local time, or ignoring daylight saving time. Sunrise, sunset, and the event must be expressed on one scale, or every boundary shifts.
6. Using sunrise and sunset for another city or date, or measuring night from midnight. Night begins at sunset, and the night hours require the next sunrise.
7. Assuming a benefic planet always gives a good hour, and overrating the hours. The condition of the planet matters more than its name; the hour is a filter, not a substitute for the chart.
11. Checklist for calculation and timing
1. State the matter and identify its natural significator.
2. Fix the place, coordinates, local date, and time zone.
3. Obtain sunrise, sunset, and the next sunrise.
4. Convert the times to minutes and compute the day and night lengths.
5. Divide each length by twelve and identify the planetary day.
6. Assign the ruler of the first hour and build the twenty-four boundaries.
7. Check the invariants: hours 1, 8, 15, 22; hour 13; hour 24.
8. Locate the required hour, check the condition of its ruler, and compare it with the chart.
9. Begin at the start of the hour and record the exact time and place.
12. Conclusion
Planetary days and hours are valuable because they are simple: seven planets, a closed sequence, and two divisions by twelve. That simplicity demands care. An hour is not sixty minutes, the day begins at sunrise, and the Chaldean order does not break at sunset. These three rules remove most errors.
The method works best as an additional layer on an electional chart. It helps to choose a day and hour that match the matter and to avoid unsuitable moments. It does not replace the analysis of the Moon, the ascendant, the houses, and the aspects, and it does not guarantee a result.
The practical order: define the action, check the chart, choose the day and hour, then verify the arithmetic. Done in that order, the hours are a precise instrument, not a decorative table.
Prepared by the [Astrobot](https://astrobot.chat) team. Based on the classical and modern astrological tradition.
endant, Moon, houses and aspects, monthly theme synthesis, timing by lunar houses and phases, comparison with natal and solar returns, limitations and common mistakes.