 The reign of this empress was marked by the opening of relations with the Sui court in 600, the adoption of the Twelve Level Cap and Rank System in 603 and the adoption of the Seventeen-article constitution in 604.The adoption of the Sexagenary cycle calendar ("Jikkan Jūnishi") in Japan is attributed to Empress Suiko in 604.At a time when imperial succession was generally determined by clan leaders, rather than the emperor, Suiko left only vague indications of succession to two candidates while on her deathbed.