From Jan 25, 2026 to Jan 29, 2026, the corresponding solar term in the Nijūshi Sekki (24 solar terms) is 大寒(Daikan), and the corresponding microseason in the Shichijūni Kō (72 microseasons) is 水沢腹堅(Sawamizu kori tsumeru).

What Is “Sawamizu kori tsumeru” (水沢腹堅)?

"Sawamizu Kōri Tsumeru" (水沢腹堅, "Stream waters freeze solid") is one of the Shichijūni Kō (72 microseasons), Japan's traditional system for dividing the year into finely observed seasonal shifts. It falls as the second microseason within the Nijūshi Sekki (24 solar terms) period known as Daikan (大寒, "the great cold"), occurring each year from around January 25th to January 29th. Its meaning can be rendered as: "Even the waters flowing through mountain streams are filled with thick, solid ice." The Shichijūni Kō represent a remarkable form of calendar wisdom, dividing the year into 72 microseasons by further splitting each of the 24 solar terms into three equal parts — each lasting approximately five days. "Sawamizu Kōri Tsumeru" falls within Daikan, the coldest period of the year, making it one of the most emblematic microseasons of the Japanese winter. During this time, even running water in streams and brooks freezes over completely — a level of cold that cuts through everything. In modern life such scenes have grown rare, but in earlier times the Japanese people observed these subtle shifts in nature with great care, using them as practical guides for farming and daily life. This poetic expression of winter's harshest depths speaks to the deep sensitivity with which the Japanese have long perceived the natural world. Once this peak of cold has passed, the seasons quietly turn toward "Harukaze Kōri wo Toku" (東風解凍) — "the east wind melts the ice" — and the first whispers of spring begin.

List of Japan’s 72 Microseasons