光天化日

Etymology
According to the scholar Hui Dong, the original (or prescriptionist) form of 化日 in the phrase might have been. In this theory, during much of the, the written corpus saw systematic censorship of the character due to  regarding the name of Li Zhi (李治), the. The character was among the most frequently-used replacements, and its legacy continued to influence later generations, who went on to use  where  would be expected even if the taboo was no longer in force.

Idiom

 * 1) in broad daylight