Many assume that East Asian fortune-telling runs on the lunar calendar, but saju and much traditional reckoning of time actually follow the 24 Solar Terms. The terms are a solar calendar that divides the year into twenty-four points by the position of the sun, each about a fortnight apart. They mark the true rhythm of the seasons and form the backbone of the months in saju.
Here is the principle. The ecliptic — the sun’s path across the sky — is divided into twenty-four equal arcs of fifteen degrees. Each term marks a turn in nature: the Start of Spring, the coming of the Rains, the waking of the insects, the grain coming into ear, the Great Heat, the White Dew, the descent of Frost, the Great Cold. The terms come in pairs that make up the seasons, and the four “beginnings” — the Start of Spring, Summer, Autumn and Winter — open each season.
This is why they matter in saju. A saju “month pillar” changes not on the first day of a calendar month but at a solar term (the twelve sectional terms, to be exact). So two people born only days apart in the “same” month can have different month pillars. The year pillar, too, turns not on January first but at the Start of Spring. To build a saju chart correctly, one must look at the solar terms, not the plain calendar date.
Beyond saju, the solar terms guided agriculture for millennia — when to sow and when to reap. And they still live on in customs and foods, such as eating certain dishes at the solstice. The terms are a living almanac of life kept in tune with the sun’s year, and a reminder that traditional fortune is rooted not in vague superstition but in real astronomy.
Seen this way, the 24 Solar Terms are a way to feel the true rhythm of the year. FortuneLeaf’s saju readings, too, set their months and years by these real solar terms. As always, this is offered for reflection rather than as a fixed fate — a way to sense your own timing, gently, in tune with the great breathing of the seasons.