What's the difference between the lunar calendar and the Gregorian calendar?

The lunar calendar is a lunar calendar, but the lunar calendar is not just a lunar calendar.

The lunar calendar handed down in ancient China is a combination of yin and yang, including the lunar calendar recorded by the moon cycle, represented by the "full moon on August 15th". It also includes "Tomb-Sweeping Day", which is represented by "solar terms" and always falls on April 5th every year.