What do you mean by having sex with beginning of spring?

Dozen spring and beginning of spring are the same meaning.

Tanchun is the same as beginning of spring, but Tanchun is the common name of beginning of spring. Beginning of spring is also called "biting spring" and "reporting spring". This festival, like many festivals, has many folk customs, such as celebrating the Spring Festival, celebrating the Spring Festival, and the custom of hitting spring cows and biting spring. Different places have different traditions and customs, so the forms of welcoming the beginning of spring are different, but to sum up, they all celebrate the beginning of the Spring Festival and place new hopes on it. Beginning of spring, also known as Da Chun, is an important solar term around the Spring Festival and a very old festival. In Xia Dynasty, beginning of spring was once the festival of the first month.

Beginning of spring is the first of the twenty-four solar terms, and it was included in the first month solar terms in the official yearbook of Ming and Qing Dynasties. The arrival time is on February 3-5 of the Gregorian calendar every year (around the first day of the first lunar month), when the sun reaches 3 15. Beginning of spring is one of the important traditional festivals of the Han nationality.