Describe time. People are accustomed to calling the sixty-year-old "sixty years old" and the elderly over sixty years old as "the sixty-year-old" or "the sixtieth year". "Huajia" is the abbreviation of "Huajiazi". The origin of this name is inseparable from the ancient Chinese stem and branch chronology. Stems and branches, namely heavenly stems and earthly branches. The heavenly stems are originally called "stems" and the earthly branches are originally called "zhi". They are a kind of counting and timing symbols that have appeared in ancient times.