At a glance
- Angular spacing
- One marker every fifteen degrees of solar longitude
Definition and scope
The twenty-four solar terms mark the Sun’s annual apparent motion and help organize seasons and intercalation. Their astronomical instants can correspond to different clock dates around the world. Weather and agricultural names describe inherited seasonal expectations; they do not guarantee rain, frost or a particular farming activity on that day.
Structure and details
The terms are spaced fifteen degrees apart in solar longitude, with minor and major terms alternating. Equinoxes and solstices provide four familiar markers. Intervals in days are not exactly equal because orbital motion is not uniform. Distinguish an event’s exact instant from the whole-day label used in everyday calendars.
Example and history
Qingming is both a solar term and a marker for commemorative customs; the winter solstice also has local food traditions. Observatory tables provide event times. Comparing the same instant in two locations illustrates time zones. In the Southern Hemisphere, inherited northern seasonal names should not be treated as local weather forecasts.
Contexts and limits
An astronomical definition does not validate additional auspiciousness, personality or dietary claims attached to a term. Farming depends on local climate, soil and crops. Cultural study can document seasonal songs and regional observations while preserving their locality. A historically northern Chinese seasonal pattern is not an invariant global schedule.
References & further reading
Historical sources document ideas and rules of their time, not empirical proof of predictive accuracy. Source notes identify the nature and scope of each reference.
- Hong Kong Observatory: The 24 Solar TermsInstitutional / reference source
Solar-term definitions and the regional seasonal background of their names.
- Hong Kong Observatory: Date and Time of the 24 Solar TermsInstitutional / reference source
Published solar-term event times must be read with the stated time standard.