Names like Ipchun (start of spring), Haji (summer solstice), and Dongji (winter solstice) sound familiar, but their exact dates and meanings are easy to mix up. Here's how and why the 24 solar terms were created, plus the date and meaning of every single one.
The 24 solar terms divide the sun's apparent path along the ecliptic into 24 equal segments of 15° of solar longitude. 0° marks Chunbun (the spring equinox), 15° marks Cheongmyeong, and so on — each term's date is fixed purely by the sun's position. That makes the system solar (essentially a solar calendar) rather than lunar, so each term falls on almost the same date every year, drifting by only a day or so.
Ancient agricultural societies along China's Yellow River relied mainly on a lunar calendar, but lunar months drift against the seasons year by year, making it hard to time sowing and harvest correctly. The 24 solar terms were devised as a sun-based system that tracks the seasons precisely, and were marked alongside the lunar calendar so farmers wouldn't miss the right moment to plant or reap.
The 24 solar terms arrived on the Korean peninsula during the Three Kingdoms period, alongside Chinese calendrical systems, and have been in use ever since. Because the original system was built around the climate of northern China, it doesn't perfectly match Korea's actual seasonal rhythm — which is part of why King Sejong commissioned the Chiljeongsan calendar in the Joseon dynasty, recalculating celestial movements specifically for Hanyang's (Seoul's) latitude. Today the terms are used less for farming and more as seasonal markers in greetings and folk customs.
The first of the 24 solar terms, marking the start of spring. Households traditionally posted good-luck phrases like "Ipchun daegil" on their doors, though the weather is still firmly wintry at this point.
Literally "rain water" — when melting snow turns to rain and the frozen ground begins to thaw.
"Awakening of insects" — when hibernating insects and frogs are said to stir awake as spring warmth truly sets in.
The spring equinox, when the sun crosses the equator and day and night are equal in length. After this, days grow longer than nights.
"Clear and bright" — often falls on or right next to Hansik. In Korea it also coincides with Arbor Day (April 5), traditionally a good time for planting trees.
"Grain rain," the last spring term — the rain around this time was crucial for seedbeds and grain germination.
Marks the start of summer, when greenery deepens and temperatures rise noticeably.
"Grain buds" — crops like barley ripen and full-scale farm work gets underway.
"Grain in ear" — traditionally the busiest time for barley harvesting and rice transplanting at once.
The summer solstice — the longest day of the year. The hottest stretch of summer actually arrives about a month later, around Daeseo.
"Minor heat," when real summer heat sets in — the monsoon (jangma) often peaks around this time too.
"Major heat," considered the hottest stretch of the year — it often overlaps with Jungbok, the second of the sambok days.
Marks the start of autumn on paper, but it usually lands during the hottest part of the year — Koreans often joke it doesn't live up to its name.
"The heat retreats" — a Korean saying goes "even a mosquito's mouth twists shut after Cheoseo," reflecting the cooler mornings and evenings that begin around now.
"White dew" — temperatures drop enough for dew to form overnight, and autumn's presence becomes unmistakable.
The autumnal equinox — day and night are equal again. After this, nights grow longer than days.
"Cold dew" — the chilly period just before dew starts turning to frost.
The last autumn term, when frost begins to fall. Peak foliage typically starts fading around the first frosts.
Marks the start of winter. Traditionally, households made kimchi for the winter (gimjang) around this time.
"Minor snow" — the first snow reports of the season tend to arrive around now.
"Major snow" by name, though in Korea the heaviest snowfalls don't necessarily line up with this exact date.
The winter solstice — the longest night of the year. People traditionally ate red bean porridge (patjuk), believing the red color warded off evil spirits, and treated the day as a kind of "mini New Year." Dongji is both a solar term and a widely observed folk holiday — see Korea's Traditional Folk Holidays for more on its customs.
"Minor cold" by name, but thanks to the Siberian high, this is often actually colder in Korea than Daehan. An old saying puts it bluntly: "Daehan froze to death visiting Sohan's house."
The final solar term — "major cold," though it's often milder than Sohan despite the name. After Daehan, the cycle starts over again with Ipchun.
Turn on "Display settings → Show solar terms" in the sanCheck app settings, and today's briefing will automatically flag it whenever a solar term or major folk holiday falls on the current day.