The twenty-third of the twenty-four solar terms, Sohan (Kor. 소한, Chin. 小寒, lit. Slight Cold), falls sometime in the twelfth lunar month. It is the first solar term occurring after the Gregorian New Year’s Day and is usually around January fifth. On this day, the sun is at an ecliptic longitude of 285°.
In ancient China, the fifteen-day period between Sohan and Daehan (Kor. 대한, Chin. 大寒, lit. Great Cold) was divided into three smaller periods of five days each. The first of these periods was characterized as one in which wild geese head northward, the second one was considered the time for magpies to build their nests, and the third was the time when pheasants cry. Being based on seasonal changes in the Yellow River valley in China, this correspondence of the period with natural events is not necessarily descriptive of the time around Sohan in Korea. For example, according to the Chinese calendar, the moderately cold temperature around the time of Sohan is supposed to drop further on Daehan, but in Korea, Sohan marks the height of winter cold.
Farming households in rural communities are busy around this time preparing for a severe cold spell usually lasting about a month until Ipchun (Kor. 입춘, Chin. 立春, Beginning of Spring). In snowy mountainous regions, people stocked up on firewood and food in anticipation of heavy precipitation, which might prevent them from leaving their villages or cut them off from supplies.