By now you have the conceptual foundation: fourteen stars from two Dippers, distributed across twelve palaces, producing a unique map of your life. The natural question is: how does the chart actually get built?
In the classical tradition, charting was done by hand — memorizing rules, converting dates, placing stars step by step. An experienced practitioner could do it in twenty minutes. A beginner might take hours.
I'm going to be direct about something: I don't think beginners should spend much time learning to chart by hand. Many traditional teachers will disagree. But reliable charting tools exist now, and the calculations are purely mechanical — fixed rules, no interpretive judgment. Spending weeks memorizing placement formulas is time better spent understanding what the placements mean.
For generating your chart, use our tool at polarastrology.com/chart. Enter your birth data, get your chart instantly. The rest of this lesson covers what you need to know to use that tool well — the inputs it expects, the practical adjustments you may need to make for your birth time, and a question about the day boundary that affects readers in the Americas.
The Inputs
A Polar Astrology chart needs four things from you:
Birth year, birth month, birth day— enter these as you'd normally tell someone your birthday, in the standard Gregorian calendar. Under the hood, the charting tool converts everything to the Taoist lunar calendar to derive the information needed for calculation. You don't need to do any conversion yourself.
Birth hour— enter the time you were born. In most cases that's just the time on your birth certificate. But read the next section before you enter it, because if your birth time falls near the boundary of a two-hour period, you may need to adjust for daylight saving time or your city's longitude. Polar Astrology works in two-hour blocks (時辰) — whether you were born at 3:15 AM or 4:45 AM, same block, same chart. But which block you're actually in can shift depending on these corrections.
From these four inputs, the charting tool calculates a Five Elements Bureau (五行局), places Polaris, cascades all fourteen major stars into position, assigns auxiliary stars, and determines your luminosity values and transformations. The mechanics — bureau calculation, Polaris placement formulas, cascade rules — are covered in the appendix for those who want them. For reading your chart, you don't need them.
Getting Your Birth Time Right
This is the most practically important section in this lesson. Don't skip it.
Our charting tool accepts a normal clock time — you enter 7:15 PM or 4:30 AM, just like any other form. But under the hood, the tool rounds that time into one of twelve two-hour blocks (時辰). 3:15 AM and 4:45 AM both fall in the same block (寅時, 3:00-5:00 AM) and produce the same chart. 4:55 AM and 5:05 AM are ten minutes apart but fall in different blocks — and produce completely different charts.
This means your exact birth minute usually doesn't matter. What matters is which two-hour block you fall in. And most of the time, that's obvious from your birth certificate. But if your birth time is anywhere near the boundary between two blocks — say, within 30 minutes of an odd hour (1:00, 3:00, 5:00, 7:00, 9:00, 11:00 AM/PM) — you need to think about two complications: daylight saving time and longitude correction. Either one can shift you from one block into the next.
Daylight Saving Time
This is the big one. If you were born during daylight saving time (summer time), your birth certificate records clock time, which is one hour ahead of standard time. That hour can easily push you across a block boundary.
For example: a birth certificate says 7:15 PM EDT (Eastern Daylight Time). Subtract one hour → 6:15 PM EST. That's 酉時 (5:00-7:00 PM). If you'd used the clock time directly, 7:15 PM would fall in 戌時 (7:00-9:00 PM) — the wrong period, the wrong chart.
How to check:look up whether DST was in effect in your birth city on your birth date. DST rules have changed throughout history and vary by location — don't assume. For US births, the website timeanddate.com has historical DST data for every city.
Longitude Correction
This is subtler but can matter. Each timezone is based on a standard meridian (for example, 75°W for US Eastern Time). If your birth city is significantly east or west of that meridian, the local solar time differs from the clock time by several minutes.
The correction is 4 minutes per degree of longitude. If your city is east of the standard meridian, add time. If west, subtract.
A practical example: Houston, Texas is at longitude 95.4°W. The Central Time standard meridian is 90°W. Houston is 5.4° west, so local solar time is about 22 minutes behind clock time. A birth recorded at 9:47 PM CDT in Houston becomes:
- Subtract 1 hour for DST → 8:47 PM CST
- Subtract 22 minutes for longitude → 8:25 PM true solar time
- 8:25 PM = 戌時 (7:00-9:00 PM)
Without the corrections, 9:47 PM would fall in 亥時 (9:00-11:00 PM) — wrong period, wrong chart.
When It Doesn't Matter
If your birth time falls solidly in the middle of a two-hour period — say, 2:30 PM, right in the center of 未時 (1:00-3:00 PM) — no reasonable correction will shift you into a different period. Don't worry about it.
The corrections matter when your birth time is within about 30 minutes of a period boundary. In those cases, generate charts for both possible periods and compare which one fits your life better. The right chart is usually obvious.
Our charting tool does NOT automatically adjust for DST or longitude — it takes whatever time you enter at face value. If you enter 9:47 PM and that was daylight saving time, the tool doesn't know to subtract an hour. You need to figure out your corrected time and enter that instead.
The Zi Hour Problem: Births Between 11 PM and 1 AM
There's an old saying in Chinese astrology: “Even immortals find it hard to judge a Zi hour chart” (神仙难断子时命).1 If you were born between 11:00 PM and 1:00 AM, you fall in the Zi hour (子時) — and this creates a specific complication worth knowing about.
The Zi hour spans midnight. That means it straddles the boundary where one calendar day ends and the next begins. A person born at 11:30 PM on March 15 and a person born at 12:30 AM on March 16 are both in the Zi hour — same two-hour block, same Life Palace position. But which daydo they belong to? The one that's ending or the one that's beginning?
For the 12:30 AM birth, there's no dispute — it's March 16 by any reckoning. But 11:30 PM is trickier. You're still on March 15 by the clock, but you've entered the Zi hour that belongs to the cycle of the next day. Different schools handle this differently, and the debate has been going on for centuries — which is presumably why the ancients warned that even immortals struggle with it.
The practical consequence: if you were born between 11:00 PM and 11:59 PM, there may be two valid charts for your birth data — one using the current day and one using the next day. Both use the Zi hour, but the different day produces a different lunar date, which can shift Polaris's position and change the entire chart.
My recommendation: if you were born in this window, generate both charts. Compare them against your life. Don't agonize over the theory — let your biography settle the question. This is the same advice I give for the adjusted day question, and for the same reason: when the tradition itself is uncertain, biographical fit is the most reliable guide.
For Readers in the Americas: The Atlantic Date Line
If you're generating a chart from the Western hemisphere, there's one more adjustment to consider. This one is more speculative than the timezone corrections — but I've tested it against real charts and I think it's worth taking seriously.
The Chinese Gan Zhi day cycle — the sixty-day cycle of Heavenly Stems and Earthly Branches — has been running continuously for thousands of years, anchored to China. In East Asia, the question of when one day ends and the next begins is simple: midnight, local time.
But what about someone born in the Americas?
The International Date Line runs through the Pacific Ocean. Cross it heading east, and you go back a day. This is a convention established for global navigation — invented in the 19th century for the convenience of European shipping. The Gan Zhi cycle predates it by millennia. And there's a case to be made that it's the wrong boundary.
Here's the argument. If you think about the Gan Zhi day as radiating outward from China in both directions, the natural place where the cycle “resets” — where the day boundary falls — would be on the opposite side of the globe from China. That's not the Pacific. That's the Atlantic.
This isn't just abstract geometry. It has a historical and anthropological logic. The Pacific Ocean was not a barrier to human civilization — it was a bridge. The ancestors of Native Americans crossed from Asia to the Americas via the Bering land bridge and coastal migration routes, tens of thousands of years before anyone crossed the Atlantic. The Asian and American continents share a continuous arc of human habitation stretching back to prehistory. If the Gan Zhi cycle traveled with human civilization as it spread eastward from China — through Central Asia, through Siberia, across the Pacific rim, and into the Americas — it would have crossed the Pacific without interruption. The natural boundary, the place where the continuous chain of eastward migration finally hit open ocean it couldn't cross, was the Atlantic.
The practical consequence: for someone born in the Americas, the Gan Zhi day may be one day ahead of their local calendar date. Your chart tool shows this as the “Adjusted day for Americas” option.
I started with this as a theoretical position. Then I tested it. I ran both the standard and adjusted-day charts for several well-known Americans whose birth data is documented from birth certificates, and compared which version better matched their known biographies. The adjusted method won in most cases. I'm not claiming this is settled. But the pattern is suggestive enough that I recommend checking the “Adjusted day” box for anyone born in the Americas — while always generating both versions to compare.
Generate Your Chart
You now have everything you need:
- Look up your birth time. If you were born during daylight saving time, subtract one hour.
- If the result is within 30 minutes of a block boundary (any odd hour), apply the longitude correction too — 4 minutes per degree from your timezone's standard meridian.
- Enter the corrected time into the charting tool.
- If you were born between 11:00 PM and midnight, try both the current day and next day.
- If you were born in the Americas, try both the standard and adjusted day options. Compare both charts against your life. One will usually feel obviously right.
Generate your chart at polarastrology.com/chart. See where your stars land. Then come back to Lesson 2 and Lesson 3and read the star and palace descriptions with your own chart in front of you. That's when this stops being a lesson and starts being yours.
— Justin Y. North
Coming next
Luminosity — How Stars Change by Palace
Notes
- The saying 神仙难断子时命 (“Even immortals find it hard to judge a Zi hour chart”) is widely cited in Chinese astrology texts. The Yuanhai Ziping(渊海子平) addresses the early/late Zi hour distinction: “The Zi hour divides into front and back — the front belongs to yin darkness, the back belongs to yang brightness” (子时分前后，前属阴晦，后属阳明). The Sanming Tonghui(三命通会) similarly notes: “Zi divides into yin and yang — the front belongs to yin, the back belongs to yang” (子分阴阳，前属阴而后属阳). ↩