Is Tomb-Sweeping Day based on the lunar calendar or the solar calendar?

There is a concept that needs to be clarified, that is, the word Qingming, which has both the concept of festivals and the concept of solar terms. As a festival, it has the content of historical inheritance or memorial custom. Because of some accidents, it is called Tomb-Sweeping Day. As a solar term, it has its scientific content. China's lunar calendar is a mixed calendar, which is based on the lunar calendar plus the solar calendar-24 solar terms. As a calendar, the twenty-four solar terms are a solar calendar, but they are not derived from the Gregorian calendar. Astronomers in China have long known the law of the solar year-the solar calendar. Of course, the international Gregorian calendar is also a solar calendar, but it does not include the lunar calendar (month).