Planetary Hours Calculator

The quick answer: the planet ruling the first hour after sunrise is the ruler of the weekday. From there, each successive hour hands the baton to the next planet in Chaldean order (Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon), cycling until the next sunrise. Twenty-four hours, seven planets, three full passes of the sequence plus three leftover hours. Those three extras push tomorrow's first hour three positions ahead, which is why the weekday ruler advances in the familiar Sun to Moon to Mars pattern rather than straight Chaldean order.

You can hear it in the weekday names. French mardi is Mars day. Italian mercoledì is Mercury day. Every language that kept the classical planet names preserves the sequence. The Hellenistic hour system leaking through 2,500 years of linguistic drift.

Scroll up. The table shows every hour of your solar day, from sunrise to the next sunrise. Each row names the ruler, the start time, and the end time. The current hour is highlighted with a live countdown.

Two things to notice. First, the hour lengths differ. Day hours (sunrise to sunset) and night hours (sunset to next sunrise) divide their respective intervals into twelve equal parts, but the daylight and nighttime rarely match. In New York on December 21, each day hour runs about 45 minutes while each night hour stretches to 75. Six months later, on June 21, the pattern flips. Hour lengths only line up with standard clock hours within a week of each equinox.

Second, the day changes ruler at sunrise, not at midnight. If you're awake at 2am on a Thursday morning, you're still operating in Wednesday's cycle (Mercury's day). Thursday starts when the Sun rises. This surprises people used to thinking in calendar days. Planetary timing runs on solar days, not civil days.

Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. That's the order. It isn't arbitrary.

The Babylonians ranked the seven visible planets by how slowly they appeared to move against the fixed stars. Saturn takes roughly 29 years to complete one trip through the zodiac. Jupiter: 12 years. Mars: about 22 months. The Sun: 1 year. Venus: 225 days. Mercury: 88 days. The Moon moves fastest, one zodiac circuit every 27 days.

Ptolemy codified the sequence in the Tetrabiblos (2nd century CE) and it stayed fixed through every subsequent tradition. The Sasanian Persians kept it. The Islamic astrologers kept it. Medieval Europe kept it. Al-Biruni, writing in the 11th century, gave the same order as William Lilly writing in 1647. Modern software that claims to use planetary hours but shuffles the sequence is doing something different. The Chaldean order is the system.

Each weekday takes its name from the planet ruling its first hour after sunrise. Romance languages preserve the Latin planetary names directly. English kept Saturday and Sunday, swapped in Norse deities for Tuesday through Friday, and gave Monday to the Moon.

When the hour matches the day (Jupiter hour on Thursday, Venus hour on Friday, Saturn hour on Saturday), the effect compounds. Traditional electional astrologers treat those windows as the single strongest election for that planet in the week. You get two of them per weekday: one in the day portion, one in the night portion, separated by roughly twelve clock hours.

Seven planets, seven distinct electional moods. The correspondences below follow Lilly's Christian Astrology (1647), Agrippa's Three Books of Occult Philosophy (1531), the Picatrix(10th to 11th century), and Al-Biruni's Book of Instruction(11th century). Each planet's dedicated guide goes further.

Four inputs: today's date, your coordinates, today's sunrise, and today's sunset (plus tomorrow's sunrise for the night portion). Example for New York on April 24, 2026.

1. Find sunrise and sunset. In New York, sunrise is 6:08am EDT and sunset is 7:43pm EDT.
2. Compute day length. Sunset minus sunrise gives 815 minutes of daylight (13 hours 35 minutes).
3. Divide daylight by 12. 815 / 12 ≈ 68 minutes. Each day hour runs about 68 minutes.
4. Repeat for the night. Sunset to next sunrise (6:06am EDT, April 25) runs 623 minutes. Divided by 12, each night hour is about 52 minutes.
5. Identify the day ruler. April 24, 2026 is a Friday. Friday belongs to Venus, so Venus rules the first hour after sunrise.
6. Walk the Chaldean sequence. Starting from Venus, count forward through Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, wrapping as needed. Your first four hours run Venus, Mercury, Moon, Saturn, starting at 6:08am EDT.
7. Keep going through the night. The 13th hour (the first hour after sunset) continues the Chaldean rotation from wherever the 12th day hour landed. No reset at sunset.

The calculator above does this for any date and city. Running through it once by hand is the fastest way to internalize what the tool is computing.

Polar regions. Above the Arctic Circle in June, the Sun never sets. Below it in December, the Sun never rises. Traditional planetary hours break down because there is no sunrise or sunset to divide. Practitioners handle this by falling back to 60-minute equal hours, or by referencing a lower-latitude sunrise. Neither is fully satisfying. Above 66 degrees latitude in June or December, treat planetary hours as symbolic rather than precise for those weeks.

Daylight Saving Time. The Sun doesn't know about clocks. When civil time jumps, sunrise and sunset in local clock time shift by an hour, and the planetary hours shift with them. The calculator handles this automatically. Any printed table you made last week stops being accurate at 2am on the transition Sunday.

Equinoxes. Around March 20 and September 22, day and night are roughly equal worldwide. Each planetary hour runs close to 60 minutes. This is the one window where planetary hours align with standard clock hours, which makes it the cleanest reference point for sanity-checking a manual calculation.

High latitudes outside polar extremes. In Reykjavik or Anchorage, summer day hours can stretch past 100 minutes while winter night hours shrink below 40. The math works; the rhythm is unusual. A 100-minute Venus hour is a long, slow Venus.

Solar position. Sunrise and sunset come from the Jean Meeus algorithm (Astronomical Algorithms, 2nd edition), the same method the US Naval Observatory uses for its published tables. Expect accuracy within seconds for civil observers below 70 degrees latitude. Above that, we bracket the refraction-corrected horizon crossing when the solution is ambiguous.

Hour division. The interval from sunrise to sunset divides into 12 equal day hours. The interval from sunset to the next sunrise divides into 12 equal night hours. Hour boundaries are kept in seconds of precision; no rounding to the nearest minute.

Chaldean rotation. The first hour of the day is assigned to the weekday ruler (Sun on Sunday, Moon on Monday, through Saturn on Saturday). From there, each successive hour moves one position along the Chaldean sequence. Twenty-four hours cover three full cycles plus three extras, which is why the first hour of the next day lands three positions further along. After seven days, you return to the same ruler. That's the mathematical origin of the seven-day week.

Privacy. The initial table is pre-rendered on our server for a default city (New York) and cached. Once you pick or save a location, all per-location computation runs in your browser. Your saved city stays on your device; we do not read your IP or your browser's geolocation on the server.

Most planetary hour tools give you a table and stop there. Two ways this one tries to earn trust.

Source-level transparency. The computation is documented: Jean Meeus solar position, Chaldean rotation from the day ruler, equal twelfths of daylight and nighttime. Per-planet guidance cites its primary sources: Lilly's Christian Astrology(1647), Agrippa's Three Books of Occult Philosophy (1531), the Picatrix (10th to 11th century), and Al-Biruni's Book of Instruction (11th century). Every electional claim traces back to the written tradition.

Electional framing, not correspondence lists. The per-planet guidance tells you what a given hour is for AND what to skip, because classical electional astrology is as much about avoidance as about timing. Mars hours aren't universally bad; they're specifically unsuited for delicate negotiation. Saturn hours aren't universally good; they're specifically unsuited for creative kickoffs. You get a working tool, not a correspondence cheat sheet.

Each hour ruler has its own history, electional catalog, and cautions. The hour pages go further than the summaries above:

• Hour of the Sun: Visibility and leadership: step into the spotlight.
• Hour of the Moon: Nurturing and home: care for family, cook, rest, or take a short trip.
• Hour of Mars: Action and drive: tackle hard tasks, exercise, compete.
• Hour of Mercury: Communication and commerce: send messages, make plans.
• Hour of Jupiter: Abundance and wisdom: seek opportunities, travel, learn, or teach.
• Hour of Venus: Pleasure and connection: beautify, socialize, reconcile.
• Hour of Saturn: Discipline and structure: organize, do focused work, plan long-term.

The hub page, planetary hours and the days of the week, pulls all seven together with the history, the Chaldean mathematics, and the weekly cycle in one place.