How the four pillars of year, month, day and hour become eight characters, and which side those characters are read from.
Write each of the four things — year, month, day and hour of birth — as a two-character Stem-Branch pair, and you get four pillars (柱) and eight characters. Hence the names Four Pillars (四柱)and Eight Characters (八字).
| Hour Pillar | Day Pillar | Month Pillar | Year Pillar | |
|---|---|---|---|---|
| Heavenly Stems | 庚 | 丁 | 戊 | 丙 |
| Earthly Branches | 子 | 卯 | 戌 | 午 |
| What changes | 2 hours | One day | Solar Term | Start of Spring |
The table above is an example showing the layout. In the traditional way it is written right to left: year → month → day → hour.
In a two-character Stem-Branch pair, the stem always comes first and the branch second. Only where "first" sits changes with the layout of a screen or a book.
Stacking them vertically is the traditional way: heaven (天) above, earth (地) below, that meaning carried straight into the layout. In horizontal writing, think of that above-and-below as lying down into left and right.
What separates the four pillars is the size of the span of time they point to. The year pillar is the widest and the hour pillar the narrowest.
| Pillar | Span it points to | Description |
|---|---|---|
| Year Pillar 年柱 | About 1 year | The whole year of birth. It changes at Start of Spring, so a birthday in January or early February takes the previous year's Stem-Branch pair. |
| Month Pillar 月柱 | About 1 month | The Solar Term span of birth. It changes at the moment a Solar Term (節) beginsand has nothing to do with the 1st of a calendar month. |
| Day Pillar 日柱 | One day | The day of birth. It changes at 23:30. The single stem here is called the day stem (日干), and destiny theory uses it as the character standing for the person themselves. |
| Hour Pillar 時柱 | 2 hours | The double-hour of birth. The day divides into twelve, with the boundaries at XX:30. |
The moments at which they change are set out in detail in The 24 Solar Terms and Metaphysical Time.
| Question | Answer |
|---|---|
| My birthday is February 1, but the year pillar shows last year's | That is correct. The boundary where the year changes is not January 1 but Start of Spring(around February 4). |
| I was born at 11:40 p.m., but the date shows the next day | That is correct. A metaphysical day begins at 23:30. |
| If the time of birth is unknown | Only the hour pillar is left blank. The three pillars of year, month and day (six characters) are fixed as usual. |
| Should the lunar birthday be entered? | No. Enter the solar (calendar) date. A Four Pillars chart is set by the position of the sun, so it has nothing to do with the lunar calendar. |
| If born overseas | The longitude of that place and the time zone then in force (including daylight saving) have to be taken into account. This feature is planned for a later release. |