「中祥」一詞，不見於禮經，翻檢《儀禮》、《禮記》二書，僅論及「大祥」、「小祥」，未見有關「中祥」之隻字片語。吳麗娛因《白孔六帖》「小祥，中祥也」之註解，加上禮經「期而小祥」、「再期而大祥」之載錄，啟其「中祥即小祥」、「中祥達喪期一半」之說。譚蟬雪因敦煌有「小祥」一年齋、「大祥」三年齋，且太傅曹元深「大祥」為三周年（三十六月），遂生「中祥」介乎「小祥」與「大祥」之間，且為兩周年之論。「中祥」為一年或二年之具體時間，有其深究之必要，期盼藉由資料之董理爬梳，釐清「中祥」之具體時間，以為後世學禮者之津筏。
歐陽脩與梅聖俞書簡「欲過中祥」之「中祥」、劉克莊〈穆陵中祥 乙丑〉疏 文，均為期年（或第十三月）之「中祥」；而龔鼎孳父亡後二周年，為其父撰詩〈四 月十五日值先大夫中祥之辰禪院佛慟述一章〉，明確道出「中祥」為二周年。前賢 或為耳目所囿，「中祥即小祥」（或初忌日）或「中祥二周年」，皆各得一偏，無法 窺其全豹。
蓋「中祥」因採「時序之中」，或採「時距之中」，及「大祥」為第二十五月（或第二忌日）或三周年，導致有不同之時間。歷來「小祥」之時間均無甚異議，但「中祥」則有第十三月、「期年」、「二年」之著錄，絕非「中祥達喪期一半」、「中祥即小祥」之說法能涵蓋；同樣「大祥」有第二十五月、「二年」、「三十六月」之著錄，「中祥」也絕非「二年」之說能賅括。「中祥」不見於禮經，為先王之所未有，可以義起也；雖有時間之異，然因禮有時中權變之宜，「中祥」喪祭之具體時間，恐難以壹齊之矣。

The term “zhong xiang” was absent in classics of rites. “Da xiang” and “xiao xiang” were described in I-Li and Li-Ji. However, there were not any words about “zhong xiang” in these two books. Wu Liyu concluded that “zhong xiang” is tantamount to “xiao xiang”, because of a note saying “xiao xiang is zhong xiang” in the book “bai kong liu tie” and records indicating “xiao xiang is carried out at the first anniversary” and “da xiang is carried out at the second anniversary” in books of rites. However, Tan Chanxue considered that zhong xiang was carried out at the second anniversary that was between “da xiang” and “xiao xiang” based on Dunhuang documents saying “xiao xiang” is a one year zhai and “da xiang” is a three year zhai. The primary purpose of this study was to resolve these conflicts on the meaning and timing of “zhong xiang”.
“Zhong xiang” was carried out right after the first anniversary or the thirteenth month after death, in Liu Ke Zhuang’s “mu ling zhong xiang yi chou” memorial and Ou Yang Xiu’s letter to Mei Sheng Yu, “yu guo zhong xiang”. On the other hand Gong Ding Zi wrote a poem “si yue shi wu ri zhi xian da fu zhong xiang zhi chen chan yuan fo tong shu yi zhang” at two years after the death of his father in which the author clearly indicated that “zhong xiang” was carried out at the second anniversary. Because of the lack of references the previous scholars could not see the whole picture and made the bias conclusions.
The timing of “zhong xiang” varied with its meaning, either the middle of time sequence or the middle of time duration and with the timing of “da xiang”, either the twenty-fifth month after death or the third anniversary. “Xiao xiang” was carried out at the thirteen month after death undoubtedly. However, “zhong xiang” might carry out at thirteen month or the second anniversary. Therefore, “zhong xiang” cannot be considered solely as the middle of mourning period or equal to “xiao xiang”. Similarly, “da xiang” might carry out at the twenty-fifth month, the second anniversary or the thirty-sixth month. Therefore, the timing of “zhong xiang” cannot be the second anniversary exclusively. Although “zhong xiang” was not described in books of rites and was not an official royal etiquettes, the etiquettes may evolve and change with time and space.