What does birthday sacrifice mean?

Birthday was widely used in ancient Han folk customs. Especially in the old days, when engaged, both men and women should write their birthdays on the Geng stickers and exchange them with each other, so as to work out whether the marriage is good or not.

In ancient times, astrologers of the Han nationality also used the year, month, day and time of a person's birth to match heavenly stems and earthly branches, and each word was combined into eight characters, so as to calculate his fate and good or bad luck in the future.