Finding your principal star — born in early February? Take the year before
updated · 5 min read
Have you ever looked up your own star and found different sites giving different answers? Most of the time the cause is not a mistake in the arithmetic but the month you were born in.
The discrepancy affects anyone born between January and the first days of February. Because the year does not turn over on 1 January in Nine Star Ki, the calendar year and the actual year come apart for just that stretch.
One formula gives the principal star from the year of birth
The calculation itself is very simple. Add the digits of the year of birth until you have a single digit, then subtract that from eleven.
- Add the digits of the year (for 1990: 1+9+9+0 = 19)
- Repeat until one digit remains (1+9 = 10 → 1+0 = 1)
- Subtract from eleven (11 − 1 = 10)
- If the result is more than nine, subtract nine (10 − 9 = 1) → One White Water
Forgetting the final subtraction is what throws the answer out. For 1990 the subtraction from eleven gives ten, and there is no tenth star.
| Year of birth (by the calendar used here) | Reduced to one digit | Principal star |
|---|---|---|
| 1984 | 4 | Seven Red Metal |
| 1990 | 1 | One White Water |
| 1995 | 6 | Five Yellow Earth |
| 1998 | 9 | Two Black Earth |
| 2000 | 2 | Nine Purple Fire |
| 2005 | 7 | Four Green Wood |
| 2010 | 3 | Eight White Earth |
Only early February changes the answer
Nine Star Ki puts the turn of the year at the Start of Spring. Anyone born before it counts, in this calendar, as born in the previous year, and takes the previous year's principal star.
Here is how much difference it makes, using the year 2000. Two days apart gives an entirely different star.
| Date of birth | Year by this calendar | Principal star |
|---|---|---|
| 3 February 2000 | 1999 | One White Water |
| 4 February 2000 | 2000 | Nine Purple Fire (the day of the term itself) |
| 5 February 2000 | 2000 | Nine Purple Fire |
The Start of Spring is often remembered as 4 February, and in some years it falls on the third. In 2025 it fell at 23:08 on 3 February. Deciding by the date alone would misplace anyone born on the third that year.
This service calculates the Start of Spring astronomically
The Start of Spring is defined as the moment the apparent longitude of the Sun reaches 315 degrees. This service calculates the time of that crossing itself, converts it to Japan time, and decides the turn of the year from that.
It is not looking anything up in a prepared table of dates, so it can decide for years no table would cover. The Four Pillars year and month pillars use the same calculation, so the two methods never disagree.
Where it cannot be settled, nothing is asserted
For a birth on the day of the term itself, whether it fell before or after the moment cannot be decided without a time of birth. This service does not ask for a time of birth.
So for anyone born on that day, the result carries a note saying that depending on the time of birth it may belong to the previous year. Saying that something cannot be determined is better than picking a side.
The monthly star comes from the principal star and the calendar month
Where the principal star shows something at the core of a person, the monthly star is taken to show something nearer the surface. It is found by sorting the principal star into one of three groups and then reading off the calendar month.
The month here also turns over at the solar terms rather than on the first. Anyone born early in a month may find the monthly star belongs to the month before as well.
Common questions
- Does a January birth count as the previous year as well?
- It does. The year turns at the Start of Spring, so anyone born between 1 January and the day before it counts as born in the previous year by this calendar. It is not only a February question.
- Should I look at the principal star or the monthly star?
- Usually the principal star is taken as the basis and the monthly star as support. The principal star is taken to show the nature you were born with, and the monthly star the nature that shows in everyday behaviour.
- Does the principal star change as I get older?
- It does not. It is fixed by the year of birth and stays the same for life. There is a separate way of reading the fortune that comes round year by year, but the principal star itself does not move.