Much has already been written since the publication of the seventh volume of The Chu Bamboo Slips of Warring States period collected at the Shanghai Museum (上海博物館藏戰國楚竹書), yet part of its contents remains undeciphered. This article attempts to elucidate the term "□日" from bamboo slip no. 9 of Wu-ming in three ways: character's form, sound and meaning. After thoroughly examining the existing research, I agree with the opinion of Feng Sheng-Jun that "□" should be defined as "□". Nevertheless, differing from the interpretation given by Feng, I believe that "□"should be read as "明" instead of "望" in the bamboo texts. The term "□日" is tantamount to "詰朝" found in Zuozhuan, which means "tomorrow". In the context of Wu-ming, "明日" indicates the date of outbreak of war.