Sixty Cycle

육십갑자 · 六十甲子

The repeating sequence of sixty stem-and-branch pairs that the whole calendar runs on.

Ten stems and twelve branches pair off in step. Because ten and twelve share a factor, they do not produce 120 combinations but sixty, and after sixty the sequence returns to its start.

This cycle counts years, months, days and hours simultaneously. It is why a sixtieth birthday is a landmark in Korea: it is the first time the year of your birth comes round again.