二十多年來，許多有關張東蓀的生卒年的記載常有出入。本文根據最近幾年最新的研究成果，把這些記載加以整理，切確指出張東蓀出生於1886年，死於1973年。這個結論得來不容易，因為張東蓀的生年雖純是史學資料和考據的問題，只要相關條件足夠，就可以解決，但張東蓀的卒年，則因政治整肅、政治壓迫、政治避諱、政治禁忌和政治疑案等等因素而無法確定。但這並不在任何意義上說張東蓀的正確生卒年可以有一組以上的問題。這就是歷史事實的實在性，以及其發生的客觀時間和歷史解釋關係間的史學問題。即使在釐清上會碰到種種方法與技術問題，但歷史事實和歷史解釋間的界線是不容混淆的。本文用該是最不可懷疑，在理論和實際上只能有一組的張東蓀的生卒年做個案，來強調即使在記載上張東蓀的生卒年有幾組，正確答案只有一組。為了提高說理的有趣性，本文也引用了二、三個隨手得來的例子，如用耶穌誕辰來標示目前全世界廣泛使用的西元紀年的錯誤，和中國的年號之複雜性問題，來加強日期的確定，並不如一般所想像的簡單。最後，本文的根本涵義在於重申本不必重申的歷史的對象的真實性。

　　　　　For more than two decades in the past, there have been divergent reports on the dates of Chang Tung-sun. This article is based on the most recent research of the past few years, through gathering and collating the results into a coherent way so as to point out precisely and accurately that Chang was born in 1886 and met his death in 1973 under most heart-rending circumstances. This conclusion on Chang's dates has not been easy to come by, because though his date of birth has been purely a question of historical evidence and investigation--as long as there are enough relevant conditions, it can be solved relatively easily--, this has not been so with respect to the date of his death, for this had involved, and in fact still involves, various elements of political purges, political oppression, political scares, political taboos, as well as politically unsolved cases of persecution, etc. However, all this can not mean that more than one set of dates for Chang's life exist, which is of course out of the question. This is an historical question between the relationship of the reality of an historical fact, its occurrence within the low of time on the one hand, and the interpretation of such a fact on the other. Even if any attempts at clarifying this relationship will encounter many methodological and technical difficulties, the line between an historical fact and its interpretations is not to be confused and compromised. This article makes use of what should be the most indubitable, both in theory and fact, dates of Chang as a case in point, to emphasize that even if there have been many divergent reports on his dates, there can only be one correct set. In order to drive home this argument, a couple of readily available instances are employed. These include the use of the (mistaken) year of the birth of Jesus as the mark of the beginning of the Christian era (AD) which is now known as the Gregorian calendar, and some extremely confusing reigning dates found in China. The simple purpose here is to stress that an apparently simple task of the dating of a lifetime as I have found in the case of Chang is not as straightforward as one would generally imagine. Last but not least, the meaning of this article is to reiterate what ought ot be a truism for an historian, namely, that there is reality in historical fact.