Is heavenly stems and earthly branches calculated by solar calendar or lunar calendar?

Accurately speaking, heavenly stems and earthly branches is calculated according to the 24 solar terms. Whether it is the solar calendar or the lunar calendar, the branch and branch will be determined according to the solar terms information. The solar calendar and the lunar calendar can be converted to each other.

For example: Gregorian calendar 198 1 7: 00 on August 23rd, corresponding to lunar calendar1981year on July 24th (chicken). This day is the first15th day after the Mid-Autumn Festival, and its main branch is Gui You Bingchen.