What the solar terms are
A solar term (节气, jieqi) is the moment the sun reaches a multiple of 15° along the ecliptic. There are 24 of them, roughly two a month, named after the weather and farming of the North China Plain. In 2016 UNESCO listed the 24 solar terms as an Intangible Cultural Heritage of Humanity.
The terms alternate between jie (节, "nodes") and qi (气, "breaths"). The twelve jie — Start of Spring, Awakening of Insects, Clear and Bright and so on — begin the twelve solar months used in BaZi, Nine Star Ki and the monthly flying stars. The twelve qi, including the equinoxes and solstices, fall in the middle of those months and decide the leap months of the lunar calendar.
The 24 terms and their meanings
| Term | Sun's longitude | Meaning |
|---|---|---|
| Minor Cold 小寒 | 285° | Coldest stretch begins |
| Major Cold 大寒 | 300° | Deepest cold of the year |
| Start of Spring 立春 | 315° | Spring begins; the feng shui and BaZi year starts here |
| Rain Water 雨水 | 330° | Snow turns to rain |
| Awakening of Insects 惊蛰 | 345° | First thunder wakes hibernating animals |
| Spring Equinox 春分 | 0° | Day and night equal |
| Clear and Bright 清明 | 15° | Clear, bright weather; time of tomb-sweeping |
| Grain Rain 谷雨 | 30° | Rain helps the grain grow |
| Start of Summer 立夏 | 45° | Summer begins |
| Grain Buds 小满 | 60° | Grain starts to fill out |
| Grain in Ear 芒种 | 75° | Grain with awns is ready; time to plant |
| Summer Solstice 夏至 | 90° | Longest day of the year |
| Minor Heat 小暑 | 105° | Heat builds |
| Major Heat 大暑 | 120° | Hottest time of the year |
| Start of Autumn 立秋 | 135° | Autumn begins |
| End of Heat 处暑 | 150° | Heat ends |
| White Dew 白露 | 165° | Dew forms on cool nights |
| Autumn Equinox 秋分 | 180° | Day and night equal again |
| Cold Dew 寒露 | 195° | Dew turns cold |
| Frost Descent 霜降 | 210° | First frost |
| Start of Winter 立冬 | 225° | Winter begins |
| Minor Snow 小雪 | 240° | Light snow |
| Major Snow 大雪 | 255° | Heavy snow |
| Winter Solstice 冬至 | 270° | Shortest day of the year |
Why the dates move
The Gregorian calendar keeps close to the solar year, so each term falls within a day or two of the same date every year — the start of spring between 3 and 5 February, the winter solstice between 21 and 23 December. The exact moment shifts by about six hours each year and jumps back after a leap year.
Questions
Why use China time?
The terms are calculated for China Standard Time (UTC+8) in the traditional calendar. The moment is the same everywhere, but the date can differ: a term at 06:00 in Beijing falls on the previous evening in the Americas. The "Your time" column converts it to your device's time zone.
Where do these times come from?
They're calculated astronomically with the open-source lunar-javascript library. Published almanacs occasionally differ by a minute because of rounding.