With respect to calendar, an error, which contradicted the rule of the lunisolar calendar had occurred in the Kyo calendar (calendar prepared by the onmyoryo (governmental agency responsible for matters related to the Way of Yin and Yang)), that usui was not included in January 1581 but shifted to the intercalary first month in which chuki should not be included.
暦の問題について、天正11年の1月の京暦の中に雨水が含まれずに本来中気が入ってはならない閏1月にずれてしまうという太陽太陰暦の原則に反した錯誤が生じていた。