Da-han  (noun) 大寒 (Chinese): Severe Cold (24th solar term), literally in Chinese “Da” 大 = big, “Han” 寒 = cold.
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In the ancient Chinese calendar also known as the “agriculture calendar”, Da-han is one of the 24 solar terms which later spread to many Asian countries. Da-han is the 24th solar term and 12th intercalating month (midpoint). Da-han begins when the Sun reaches the celestial longitude of 300° and ends when it reaches the longitude of 315°. Da-han more often refers in particular to the day when the Sun is exactly at the celestial longitude of 300°. In the Gregorian calendar, Da-han usually begins around 20 January and ends around 4 February. In ancient China, Da-han was divided into three periods: in the first period 鸡乳 (ji-ru); hens began to hatch their chicks. During the second period 征鸟厉疾 (zheng-niao li-ji), birds such as eagles and owls are in a state of extreme predatory ability, hovering around the sky to find food in order to enhance their energy to resist the cold. In the last period 水泽腹坚 (shuize-fujian), the ice is frozen within the center of the water, children can enjoy ice skating on the river. Da-han is the last term of the 24 solar terms in China.  After Da-han the Spring will usher in a new year’s solar cycle. The next solar term will be Li-chun (Beginning of Spring).
Natural flowers, trees, birds and animals all live and move according to a certain season. Their activities are closely related to climate change.  Each period 候 in a Jie-qi 节气 is associated with a flower 花信. During Da-han, the first period is associated with winter daphne 瑞香 , second with orchids 兰花, and the third period with caudate sweetleaf flower 山矾.  In addition to these three flowers, there are cherry blossoms, winter jasmine flowers, Yulan magnolia, lilac flowers, etc that bloom during Da-han.
Since ancient times, Da-han has been a solar term for agricultural purposes in the lunar calendar. Da-han is still remembered and celebrated as a Chinese traditional festival.