Is it because the date of the lunar calendar (old calendar) is different every year, so the date of the solar calendar is used to determine the 24 solar terms?

The lunar calendar is mainly arranged according to the moon phase cycle. It has 12 moons a year, about 354 or 355 days. The solar calendar is called the solar calendar, which is calculated according to the movement period of the earth around the sun. The Gregorian calendar year is approximately equal to the tropic year, one year 12 months. This "month" has nothing to do with the first lunar month. The month and date of the solar calendar are very consistent with the position of the sun on the ecliptic. According to the date of the solar calendar, we can clearly see the changes of cold and warm seasons in a year. But every month, you can't see the new moon, the new moon, the new moon. According to the position of the sun on the ecliptic, the 24 solar terms are divided into 24 seasons and climates that reflect the natural phenomena and farming season characteristics in a certain area of China (represented by the middle and lower reaches of the Yellow River). Twenty-four solar terms are a supplementary calendar formulated by China in ancient times to guide farming, which has little connection with the lunar calendar.