BaZi was designed around the Sun, not around the clock on your wall. Your hour pillar — and near midnight, your day pillar — depends on where the Sun actually was when you were born. Clock time can be off by half an hour or more, so Fate Hall corrects it.
Why the clock and the Sun disagree
Three separate effects push clock time away from solar time:
- Longitude. A time zone shares one clock across a wide band of land, but the Sun crosses each meridian at a different moment. Every degree of longitude is four minutes of solar time. Seoul uses the clock of 135° East but sits at about 127° East, so the Sun reaches its highest point around 32 minutes after clock noon.
- The equation of time. Because the Earth's orbit is an ellipse and its axis is tilted, the true Sun runs up to about 16 minutes ahead of the average ("mean") Sun in early November and up to about 14 minutes behind it in February.
- Daylight saving time. Summer time moves the clock an hour ahead of standard time without moving the Sun. Many countries have also changed their time zones over the years — Korea, for example, used UTC+8:30 for part of the 20th century.
Longitude correction around the world
The correction is simply four minutes for every degree between your birthplace and the central meridian of its time zone. A minus sign means the Sun is behind the clock, so solar time is earlier than clock time.
| City | Longitude | Time zone meridian | Correction to clock time |
|---|---|---|---|
| Seoul | 127.00° E | 135° E (UTC+9) | −32 min |
| Tokyo | 139.75° E | 135° E (UTC+9) | +19 min |
| Beijing | 116.39° E | 120° E (UTC+8) | −14 min |
| Singapore | 103.86° E | 120° E (UTC+8) | −65 min |
| Mumbai | 72.86° E | 82.5° E (UTC+5.5) | −39 min |
| London | 0.12° W | 0° (UTC) | 0 min |
| Paris | 2.33° E | 15° E (UTC+1) | −51 min |
| Madrid | 3.68° W | 15° E (UTC+1) | −75 min |
| New York | 73.98° W | 75° W (UTC−5) | +4 min |
| Toronto | 79.42° W | 75° W (UTC−5) | −18 min |
| Chicago | 87.75° W | 90° W (UTC−6) | +9 min |
| Los Angeles | 118.18° W | 120° W (UTC−8) | +7 min |
| Sydney | 151.19° E | 150° E (UTC+10) | +5 min |
Within the same country the correction can differ a lot: western Spain and western China are more than an hour behind the clock in solar terms. That is why Fate Hall asks for your birth city rather than just the country.
The equation of time
On top of the longitude correction, the equation of time changes slowly through the year. The values below are calculated with the same formula Fate Hall uses and are almost the same every year.
| Month | 1st | 15th |
|---|---|---|
| Jan | −3.6 min | −9.4 min |
| Feb | −13.6 min | −14.1 min |
| Mar | −12.3 min | −8.9 min |
| Apr | −3.8 min | 0.0 min |
| May | +2.9 min | +3.6 min |
| Jun | +2.1 min | −0.5 min |
| Jul | −3.9 min | −6.0 min |
| Aug | −6.4 min | −4.5 min |
| Sep | 0.0 min | +4.8 min |
| Oct | +10.3 min | +14.2 min |
| Nov | +16.5 min | +15.4 min |
| Dec | +11.0 min | +4.9 min |
The three time bases in Fate Hall
- Longitude-corrected (local mean time) — the default. Daylight saving and historical time zones are removed using your browser's time zone database, then the longitude correction is applied.
- True solar time — longitude correction plus the equation of time. This is the most literal reading of "where was the Sun".
- Clock time as is — no correction, for readers who follow schools that use the civil clock.
Practitioners disagree on which basis is best, so the BaZi screen includes a panel that shows your pillars under every basis side by side. In most charts they agree; when they differ, the panel tells you which pillar changes, and you can choose the basis that matches the tradition you follow or the time on your birth certificate.
When it matters
The correction only changes a pillar when your birth time is close to a boundary: the start of a two-hour period (every odd hour on the clock, such as 01:00, 03:00 or 13:00), midnight, or — for the month and year — the moment of a solar term. If you were born at 14:10 in Seoul, for example, the solar time is about 13:38, which still falls in the same double hour. Born at 13:20, solar time is about 12:48, and the hour pillar moves back one period.
Common questions
I only know my birth time roughly. Is the correction still worth it? Yes — it is a systematic shift, not a fine detail. But if your time is uncertain by more than the correction, check the time-basis panel, and treat the hour pillar as the least certain part of your chart.
Does Fate Hall need my exact address? No. The nearest city is enough: within one city the difference is well under a minute. Your birthplace stays in your browser and is never sent anywhere.
Related guides
- The Rat Hour RuleWhy births between 23:00 and midnight can have two different day pillars, how the early and late Rat-hour rules work, and the full table of hour pillars.
- Luck PillarsHow the ten-year Luck Pillars are built from your month pillar, why they run forward or backward, how the starting age is calculated from the solar terms, and how to read them.
- The Twelve Earthly BranchesThe twelve branches from Zi (Rat) to Hai (Pig): their element, solar month, double hour and hidden stems, and the harmonies and clashes between them.