《禮記•曲禮上》：「外事以剛日，內事以柔日。」葉國良先生已撰文證實《春秋》經傳與祭祖相關之事多用柔日。本文以《春秋》經傳為範圍，爬梳相關記載，將可能選用柔曰事務分為祭祀與政治二類。祭祀事務如喪之告廟、郊祭、雩祭選用柔日比例皆100%。政治事務包括新君即位、冊立與朝宗廟、國君與卿大夫或卿大夫間之盟、國君與卿大夫出奔他國等，其中新君即位、冊立與朝宗廟可合併計算，柔日比例63.64%。一國之內同盟與出奔，選用柔日比例分別達72.73%與82.35%。本文探究「政治」事務偏用柔日之由，乃因新君即位、盟誓、出奔皆與祭奠祖先或神靈關聯。知「內事以柔日」之說不僅可信，且進一步得知選用柔日事務大凡與祭祀相關。

The part one in Quli in the Records of Rites notes that the odd days used for external affairs, and the even ones used for internal affairs. Ye Guoliang verifies that internal affairs recorded in the Spring and Autumn Annals Jingzhuan and ancestor worship used even days often. This study is based on the Spring and Autumn Annals Jingzhuan to clarify the related records and divide the affairs which possibly used the even days into two categories— ancestor worship and politics. Even days are used 100% chance in ancestor-worshipping affairs, such as telling deities of holding mourning ceremony, rural festival, or praying for rain. Political affairs includes new emperor ascending the throne and worshiping at the ancestral shrine, which can be calculated together and the even days they used is 63.64%, the alliance between the emperor and officials or officials and officials, which is calculated as 72.73%, and the emperor and officials absconding to other countries, which is calculated as 82.35%. This study probes into the reasons why political affairs mentioned above used even days often. This research can not only make sure the saying that internal affairs used even days, but also know that using even days was related to sacrifices.