傳世文獻言「外事以剛日，內事以柔日。」外事者，郊外之事，如田獵、戰爭；內事者，郊內之事，如冠、昏、喪、祭諸事；剛日為甲、丙、戊、庚、壬，柔日為乙、丁、己、辛、癸。殷周金文的內容，或見祭祀、冊命、賞賜、媵辭、軍事戰爭、田獵與自作器物等，其間載有紀日干支者甚多，據目前已發表的資料觀察，殷商時期祭祀先王先公或先妣大多在其日干名之日舉辦，於賞賜、祭祀、田獵銘文等內容，亦無剛日、柔日的使用。兩周時期有關軍事、戰爭的內容，其干支多為剛日，然亦見柔日，至於其他內容則是剛日、柔日並用；此外，若涉及鑄作鐘鎛，「丁亥」日則較常出現。

Some handed-down documents once proposed that “Foreign affairs should be handled on vigorous days and internal affairs on soft days.” Foreign affairs refer to such suburban affairs as field hunting and warfare, while internal affairs are urban affairs like crowning ceremonies, marriages, funerals, sacrifices, etc. The vigorous days are Chia, Bing, Wu, Geng, and Ren, and the soft days are Yi, Ding, Ji, Xin, and Gui. Bronze inscriptions in the Yin and Zhou Periods are seen in sacrifices, decrees, rewards, dowry speeches, military warfare, field hunting, self-made utensils, etc., which feature many inscriptions about Heavenly Stems and Earthly Branches. According to the published data, sacrifices for deceased elder male and female figures were often held on Heavenly Stem days, and vigorous days and soft days regarding the contents of bronze inscriptions of rewards, sacrifices, and field hunting were not used. As for military affairs and warfare in the Western and Eastern Zhou Period, the Heavenly Stems and Earthly Branches often represented vigorous days and occasionally soft days. Vigorous days and soft days were used simultaneously for other contents. Furthermore, the days of Ding and He often appeared when cast bells and bo were involved.