Birth Time in BaZi: How to Determine It When It’s Unknown
Birth time provides the fourth pillar of a BaZi chart—the Hour Pillar. Many people know it only approximately: “early in the morning” or “in the afternoon.” Let’s explore how the Chinese divide the day, why clock time sometimes needs adjusting, and what to do if your birth time is unknown.
The twelve Chinese hours
The Chinese day is divided into 12 hours, each lasting two conventional hours. Each is named after an Earthly Branch:
| Hour | Branch | Time |
|---|---|---|
| Rat | 子 | 23:00–01:00 |
| Ox | 丑 | 01:00–03:00 |
| Tiger | 寅 | 03:00–05:00 |
| Rabbit | 卯 | 05:00–07:00 |
| Dragon | 辰 | 07:00–09:00 |
| Snake | 巳 | 09:00–11:00 |
| Horse | 午 | 11:00–13:00 |
| Goat | 未 | 13:00–15:00 |
| Monkey | 申 | 15:00–17:00 |
| Rooster | 酉 | 17:00–19:00 |
| Dog | 戌 | 19:00–21:00 |
| Pig | 亥 | 21:00–23:00 |
The Hour’s Heavenly Stem depends on the Day’s Stem. On 甲 and 己 days, the Hour of the Rat is 甲子; on 乙 and 庚 days, it is 丙子; on 丙 and 辛 days, it is 戊子; on 丁 and 壬 days, it is 庚子; and on 戊 and 癸 days, it is 壬子. The Stems then continue in order.
Example: Twins Robin and Maurice Gibb
The example of twins clearly illustrates how important birth time can be. Robin and Maurice Gibb, members of the Bee Gees, were born on December 22, 1949, in Douglas on the Isle of Man. Robin was born in the Hour of the Ox, while Maurice was born in the Hour of the Tiger. Their Year, Month, and Day Pillars are identical: 己丑, 丙子, 丙戌. Both have Yang Fire 丙 as their Day Master, born in winter, in the Month of the Rat, when Fire is weak. Only the Hour Pillar differs—and that is enough to give their charts different structures.
Robin, Hour of the Ox 己丑. His Hour Pillar adds more Earth. Earth represents Output for Fire and drains its strength. The chart becomes so weak that Fire stops resisting and “follows” its surroundings—this is a special “Follow the Leader” structure.
Maurice, Hour of the Tiger 庚寅. The Tiger represents Wood and also contains hidden Fire. Wood represents Resources for Fire, giving it support. This Fire can no longer “follow”; instead, it is simply weak Fire that needs support.
This means the brothers have different useful elements and respond differently to the same Luck Pillars and years. Their lives also unfolded differently. Maurice died in January 2003 at age 53 following surgery on his small intestine—an organ associated with the Fire element in Chinese tradition. Robin outlived his brother by almost nine years and died in May 2012. A two-hour difference in the Hour Pillar—and two different charts.
Clock time and solar time
Chinese hours are tied to the Sun: the Hour of the Horse is the period around true noon. But your watch shows the time in your time zone, which often differs from solar time. In Moscow, solar noon occurs around 12:30, while in Vladivostok it occurs around 13:10.
Two other factors affect the calculation:
- Daylight saving time. If clocks were moved forward for the summer in your birth year, one hour must be subtracted.
- Time set ahead of or behind solar time. For example, in the world’s largest country by area—the USSR and later Russia—clocks ran one hour ahead of standard time for many years. So-called “decree time” was introduced in 1930, moving clocks throughout the country forward by one hour, and the rules changed several times afterward. Turkey has kept daylight saving time permanently since 2016, so its clocks remain advanced year-round. Iceland has used UTC+0 since 1968, although its longitude places it closer to UTC−1. In winter, the country’s time is artificially behind the Sun, but at Iceland’s latitude, the nearly 24-hour summer days compensate for this. In March 1940, Spain moved its clocks forward by one hour to use the same time as Germany. The measure was presented as temporary, but the hour was never reversed after the war. Spain still uses Central European Time, like Berlin and Paris, even though geographically it “should” use Greenwich time, like London and Portugal.
The good news is that this adjustment often makes no difference: a Chinese hour lasts a full two conventional hours. It matters mainly if you were born close to a boundary, for example at 14:50 or 15:10. Enter your place of birth in the BaZi calculator, and it will apply the necessary adjustments.
Early and late Rat
The Hour of the Rat is unusual: it begins at 23:00 and ends at 01:00, spanning two calendar days. Some schools consider the new day to begin at 23:00, while others divide the Hour of the Rat into “late Rat” (23:00–00:00) and “early Rat” (00:00–01:00). If you were born during this period, compare both charts: they will have different Day Pillars. The calculator on our site changes the day at midnight.
If your birth time is unknown
Without the hour, you can calculate three of the four pillars. The most important pillar in BaZi is the Day Pillar, and you will still know it. The Hour Pillar usually adds around 10–20% of the information: about children, later life, and hidden personality traits. Of course, in some cases, such as the example of Robin and Maurice Gibb, the Hour Pillar can change the structure of a BaZi chart, but this is more the exception than the rule.
If you know at least an approximate time range, you can try to narrow it down:
- Through life events. Generate a chart for each possible hour and see which one best explains the events of your life. The difficulty is that adjacent hours often make little difference to the overall picture.
- Through sleeping position. This little-known method is taught in courses by Dr. Manfred Kubny, a German sinologist and one of Europe’s leading BaZi experts. A person’s habitual sleeping position is believed to be connected to their birth hour.
| Habitual sleeping position | Likely birth hour |
|---|---|
| On your back | Rat (23:00–01:00), Horse (11:00–13:00) |
| On your stomach | Rabbit (05:00–07:00), Rooster (17:00–19:00) |
| On your side | All other hours |
For example, if someone is known to have been born at night and prefers sleeping on their back, the Hour of the Rat is the most likely. If they sleep on their side, it may be the Hour of the Ox or Tiger. Of course, this is a clue, not proof: we turn over in our sleep, so the relevant position is the one in which it is easiest to fall asleep.
Birth time and date selection
The Year and Day Pillars are the most important for personal Day Stars, so the Personal Calendar works even without an exact birth time. However, the more complete your BaZi chart, the more precisely dates can be assessed for important undertakings. Even if your birth time is unknown, you can find your personal stars using your date of birth and use the auspicious date finder for a specific undertaking.
Frequently asked questions
I was born at exactly 15:00—which hour applies to me?
At the boundary between hours, solar time is the deciding factor. In Moscow, 15:00 clock time is approximately 14:30 solar time, so it is still the Hour of the Goat. In other cities, the answer may differ.
Can I simply use noon if my birth time is unknown?
It’s better not to: an invented Hour Pillar will distort the analysis. Working with three pillars is more reliable.
Does birth time change the Day Master?
No. The Day Master is the Day’s Stem, and the hour does not change it. The exception is a birth between 23:00 and midnight, when different schools assign the day differently.
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