That sixty-year-cycle was an inherent cycle similar to cycle of days

months and years was put forward based on the astronomy background of sixty-year-cycle

relationship between cycles and inspiration by the theoretical structure of Huangdi Neijing. A broad scope of astronomy determined the birth of sixty-year-cycle which was less stable due to the variation of larger cycle. So

if we want to forecast by using sixty-year-cycle

we should face and take advantage of its irregularity.