Tomb-Sweeping Day is 15 days after which solar term?

Tomb-Sweeping Day is Tomb-Sweeping Day, which originally meant fifteen days after the vernal equinox.

From 65438 to 0935, the government of the Republic of China designated April 5th as a national statutory holiday in Tomb-Sweeping Day, also known as the National Tomb Sweeping Festival. On May 20th, 2006, with the approval of the State Council, Tomb-Sweeping Day was listed in the first batch of national intangible cultural heritage. Tomb-Sweeping Day, also known as the outing festival, is one of the traditional festivals in China, and it is also one of the most important sacrificial festivals. It is at the turn of mid-spring and late spring, that is, 104 days after the winter solstice. This is the day to worship ancestors and sweep graves.