The solar terms — the twelve days on which the month turns
updated · 5 min read
The twenty-four solar terms divide the Sun's path into twenty-four and give each turn of the season a name. They run from the Start of Spring through Rain Water and the Awakening of Insects, coming full circle in a year. They alternate between what are called sectional terms and mid terms.
Twenty-four divisions means fifteen degrees each. Every fifteen degrees the Sun moves, the next term begins — about fifteen days. So terms arrive every half month, and because they alternate, the sectional ones come about a month apart.
The Four Pillars and Nine Star Ki use only the sectional terms to divide the months. The mid terms are not used, which leaves twelve boundaries.
The twelve that divide the months
| Term | Roughly | The month it begins |
|---|---|---|
| Start of Spring | 4 February | Tiger |
| Awakening of Insects | 6 March | Rabbit |
| Clear and Bright | 5 April | Dragon |
| Start of Summer | 6 May | Snake |
| Grain in Ear | 6 June | Horse |
| Minor Heat | 7 July | Goat |
| Start of Autumn | 8 August | Monkey |
| White Dew | 8 September | Rooster |
| Cold Dew | 8 October | Dog |
| Start of Winter | 7 November | Pig |
| Major Snow | 7 December | Rat |
| Minor Cold | 6 January | Ox |
The dates are approximate because they shift every year. Being fixed by the position of the Sun, they do not line up with calendar dates, and move by a day either way depending on the year.
The mid terms are not used
The other twelve are the mid terms: Rain Water, the spring equinox, Grain Rain, Grain Full, the summer solstice, Major Heat, the End of Heat, the autumn equinox, Frost Descent, Minor Snow, the winter solstice and Major Cold. The famous ones — the equinoxes and solstices — are among these.
Many of the mid terms sit closer to how a season actually feels. The summer solstice is the longest day and the winter solstice the shortest. As markers for daily life they are the more familiar. They are not used to divide the months; their part is different.
The equinoxes and solstices are large markers in the feel of a season, and they are not used to divide the months in the Four Pillars. Western astrology takes the vernal equinox as its origin, so take care not to mix the two.
Born early in a month? You may fall in the one before
Because the terms fall around the sixth to the eighth, anyone born early in a month counts as the previous month by this calendar. Born on 3 March, you fall before the Awakening of Insects that year and are calculated as born in February.
When your calendar month changes, so does the sign of the month pillar. Since that pillar reads work and where you stand, the effect is not small. Anyone born early in a month would do well to check it properly once.
It is the same thinking as the Start of Spring for the year. From 1 January to the day before it counts as the previous year; the mechanism is identical.
This service calculates the date and time of all twelve terms from the position of the Sun. It is not consulting a prepared table, so it can decide for any year of birth. For a birth on the day of a term, it shows a note rather than asserting a side.
Common questions
- Which month do I fall in by this calendar?
- A reading on this service shows the preceding term and the month branch in the result. Anyone born early in a month can see how they are treated there.
- Is the spring equinox not used?
- Not in the Four Pillars, since it is a mid term. Western astrology takes the vernal equinox as its origin, and the systems are different, so do not mix them.
- Are the term dates the same every year?
- They are not. Being fixed by the position of the Sun, they move by a day either way. In some years the time has to be taken into account.