UtilibyWritten by the Utiliby editorial team · Last updated October 15, 2026 · Rules and formulas reviewed October 2026
What this free online planetary hours calculator does
Planetary hours are one of the oldest ways of connecting time with the seven classical planets. The idea is simple: each day belongs to a planet, each hour belongs to a planet, and the two follow a fixed pattern. This free online planetary hours calculator turns the pattern into a table for any date and place. It finds sunrise and sunset, divides the day and the night into twelve hours each, names the ruling planet of every hour and highlights the hour you are in.
It also works as a Chaldean planetary hour tracker and shows planetary hours for the night as clearly as the daytime ones. Everything runs in your browser, and your location is never uploaded.
How to use the calculator
- Choose a date, or leave today's date.
- Pick a city from the list. Its latitude, longitude and UTC offset are filled in for that date. For another place, choose Custom and type the values, or press Use my location.
- Read the tiles: day ruler, sunrise, sunset, the length of a day hour and a night hour, and the hour now in effect.
- Look at the clock. Sunrise is at the left, the 12 day hours run over the top to sunset, and the 12 night hours run back underneath in slightly lighter colours. Each hour is coloured by its planet, and a line marks the selected time.
- Use the table for exact start and end times.
- Copy, download or print the hours.
The order of the planets and the day rulers
Planetary hours rely on two sequences. The Chaldean order lists the planets by how slowly they move through the sky: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. The day rulers are the planets that rule the first hour of each weekday: Sun for Sunday, Moon for Monday, Mars for Tuesday, Mercury for Wednesday, Jupiter for Thursday, Venus for Friday and Saturn for Saturday.
To find the planet of any hour, start with the day ruler for hour 1 and step through the Chaldean order, one planet per hour, wrapping round after the Moon. On Sunday the first hours are Sun, Venus, Mercury, Moon, Saturn, Jupiter, Mars, then Sun again. By the end of the 24th hour you have moved 23 places, which lands you exactly one planet before the ruler of the next day, so the rhythm continues without a break.
Why the hours are unequal
Planetary hours are temporal or seasonal hours. A day hour is one twelfth of the time between sunrise and sunset, and a night hour one twelfth of the time between sunset and the next sunrise. In midsummer at a high latitude a day hour may be 80 minutes and a night hour 40. At the equinoxes they are close to 60 minutes. Near the equator the difference is small all year.
Sunrise here is the moment the top edge of the Sun appears at the horizon, using the usual correction for refraction. Real sunrise also depends on altitude and the local skyline, so a few minutes' difference from your window is normal.
Traditional associations
| Planet | Day | Traditionally linked with |
|---|---|---|
| Sun | Sunday | Vitality, leadership, recognition |
| Moon | Monday | Home, family, the public, rest |
| Mars | Tuesday | Courage, effort, competition |
| Mercury | Wednesday | Study, communication, trade |
| Jupiter | Thursday | Learning, growth, generosity |
| Venus | Friday | Relationships, art, pleasure |
| Saturn | Saturday | Discipline, structure, endings |
Treat these as part of a cultural tradition. They are used for planning and reflection by people who follow astrology or ceremonial practice, and they do not predict how any hour will go.
How people use planetary hours
In the Hellenistic and medieval traditions, the planetary hour was used mainly in electional astrology, where a start time is chosen for a task so that the ruling planet suits it. Later ceremonial and magical writers adopted the system for the timing of rituals, and some modern readers use it simply as a daily rhythm: a Mercury hour for writing and study, a Venus hour for a social call, a Saturn hour for tidying and planning. None of this needs belief in astrology to be useful as a habit, since choosing a time for each type of task is an old and sensible way to organise a day. The calculator gives you the times so that you can decide how, or whether, to use them.
Worked example
Suppose sunrise is at 06:30 and sunset at 18:30 on a Sunday. The day is 12 hours long, so each day hour is exactly 60 minutes. Hour 1 runs 06:30 to 07:30 and belongs to the Sun, hour 2 to Venus, hour 3 to Mercury and hour 4 to the Moon. The night starts at 18:30 with hour 13. Counting on from the Sun, hour 13 is Jupiter (hour 8 is the Sun again, then Venus, Mercury, Moon, Saturn, Jupiter).
Common mistakes
- Using clock hours. Planetary hours do not start on the hour.
- Using midnight as the start of the day. The planetary day starts at sunrise, so before sunrise the day ruler is still the previous day's.
- Using the wrong offset. Check the UTC offset when you enter a place by hand, especially in daylight saving seasons.
- Expecting precision beyond the method. A minute or two either way is normal.
Privacy, limits and responsible use
The calculator runs in your browser. If you press Use my location, your browser asks permission and the coordinates stay on your device. Your last place is saved in local storage so the page reopens where you left it, and it is never sent to a server. Sunrise and sunset come from a standard approximate formula. The tool is meant for study and entertainment and is not a substitute for official timekeeping. Astrology is an interpretive tradition, not a validated predictive science, and nothing here replaces advice from a doctor, lawyer, financial adviser or mental-health professional.
Frequently asked questions
What are planetary hours?
Planetary hours are a traditional system that divides the time from sunrise to sunset into 12 equal parts, and the time from sunset to the next sunrise into 12 more. Each hour is ruled by one of the seven classical planets in a fixed order.
How do I use this free online planetary hours calculator?
Pick a date and a place, or enter your latitude, longitude and UTC offset. The tool shows the day ruler, sunrise, sunset, the length of day and night hours and a table of all 24 hours with their planets. The current hour is highlighted.
What is the Chaldean order of the planets?
Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, then it repeats. It runs from the slowest planet to the fastest as seen from Earth.
Which planet rules the first hour of each day?
The ruler of the day: the Sun on Sunday, the Moon on Monday, Mars on Tuesday, Mercury on Wednesday, Jupiter on Thursday, Venus on Friday and Saturn on Saturday. The day names reflect this.
Why are planetary hours not 60 minutes long?
Because they are one twelfth of the actual daylight or night. In summer the day hours are longer than 60 minutes and the night hours shorter, and the reverse in winter. Only at the equinoxes are they close to an hour each.
How do I find the night planetary hours?
The night hours start at sunset and end at the next sunrise. The calculator uses the following sunrise to split the night into 12 equal hours, and continues the planetary order from the 12th day hour.
How are sunrise and sunset calculated?
With a standard low-precision solar position formula, using the date, your latitude and longitude, and a solar altitude of 0.833 degrees below the horizon to allow for the Sun's radius and atmospheric refraction. It is usually within a minute or two of published tables.
Why does the tool need my UTC offset?
So that the times are shown in your clock time. Choosing a city fills in the offset for that date. Enter it yourself for a place that is not listed.
Does it handle daylight saving time?
It uses the offset you give for the chosen date. A clock change inside the same day is not applied, which is rare.
What if the sun does not rise or set?
Near the polar circles there are days with no sunrise or sunset, so planetary hours cannot be worked out in the usual way and the tool says so.
Can I see the planetary hour right now?
Yes. Leave the time box empty and the current hour is highlighted and refreshed every half minute. Type a time to check another moment.
What is the planetary hour of the night before sunrise?
Before sunrise, the moment still belongs to the night of the previous day, so the ruling day is the previous day. The tool handles this for you.
What are the planets said to be good for?
Traditional lists link the Sun with leadership and recognition, the Moon with home and family, Mercury with study and communication, Venus with relationships and art, Mars with courage and effort, Jupiter with learning and growth, and Saturn with discipline and endings. These are traditions, not facts.
Can I download or print the hours?
Yes. Download gives a CSV of the 24 hours. Print or save outputs only the summary, clock and table for your place and date.
Is my location stored or sent anywhere?
No. If you use the location button your browser asks permission and the coordinates stay in this page and in local storage on your device. Nothing is sent to a server.
Is it accurate enough for ritual timing?
It is intended for study and planning. For timekeeping that matters, check against a local almanac or an official sunrise and sunset table.
Is the tool free?
Yes, it is a free online calculator with no sign-up.
Sources and further reading
- NOAA Global Monitoring Laboratory, Solar Calculation Details and the Sunrise and Sunset Calculator (gml.noaa.gov), for the solar position and sunrise equations.
- Jean Meeus, Astronomical Algorithms, 2nd edition (Willmann-Bell, 1998), chapters on the Sun and the equation of time.
- Vettius Valens, Anthology, translated by Mark Riley (2010), on the planetary hours and the ruler of the day.
- Ptolemy, Tetrabiblos, translated by F. E. Robbins (Loeb Classical Library, 1940), on the order of the planets.
- Dorotheus of Sidon, Carmen Astrologicum, translated by Benjamin Dykes (Cazimi Press, 2017), on the hours of the planets.
Sources were consulted in October 2026. Standards and rules can change, so always check the official page for your situation.