Are solar terms calculated by lunar calendar or solar calendar?

Solar terms are calculated according to the solar calendar.

The 24 solar terms are divided according to the solar calendar. The twenty-four solar terms reflect the annual apparent movement of the sun, so the date of the solar terms is basically fixed in the current Gregorian calendar. The 24 solar terms in China are: beginning of spring, rain, sting, vernal equinox, Qingming, Grain Rain, Long Summer, Xiaoman, Mangzhong, Summer Solstice, Little Summer, Big Summer, beginning of autumn, Early Summer, White Dew, Autumn Equinox, Cold Dew, Early Frost, beginning of winter, Light Snow, Heavy Snow, Winter Solstice, Slight Cold.