Shishuo Xinyu4§80 states Xi Zuochi held high rank in Huan Wen's provincial government before the age of thirty. Huan Wen became Inspector of Jing Province following the death of Yu Yi (庾翼) in 345, indicating a birth year after 316 for Xi Zuochi. Shishuo Xinyu is not a reliable historical text, but this is the closest we have to a record of Xi Zuochi's birth. See Mather, p 142.
Xi Zuochi's death has traditionally been dated to October or November 384 (10th month of the 9th year of the Tai'yuan era), as recorded in the Tang-eraVeritable Records of Jiankang (Jiankang Shilu), p 275 (vol.09). However, a single line of text in Xi Zuochi's Records of the Elders of Xiangyang records the death of Zhu Xu (朱序) in 393. The editors of the modern annotated version of this work treat the line as a later interpolation (see Shu Fen and Zhang Lingchun, p 407 n 4). By contrast, American Xi Zuochi expert Andrew Chittick adds at least nine years to Xi Zuochi's lifespan (see Chittick, p 41 n 39). Chittick's theory has gained some currency in English-language sinology, being adopted for example by J. Michael Farmer (p 55), who gives vital dates of ca. 318 – ca. 395. The traditional dating of 384 remains the standard for Chinese-language studies.
Many sources have Xingyang (滎陽) for Hengyang (衡陽) as the locale of Xi Zuochi's quasi-banishment, but this was politically impossible, as Xingyang was not only not under Huan Wen's jurisdiction, but in fact was not even controlled by the Jin dynasty until after Huan Wen's death. See Cheng Yanzhen's (程炎震) commentary to Shishuo Xinyu4§80, p 217 n 2, and Wu Shijian's (吳士鑑) commentary to the Book of Jin, included in the same note.
