In this paper, I shall do a comparative study of the understanding of temporality in Laozi and Heidegger. First of all, I shall start from a newly discovered fact that in the book of the Laozi, the word "heng", a key word in understanding Laozi's concept of temporality of dao, was missing during the past 2000 years. In most editions of the text, a synonym, "chang", was substituted, which may refer to a totally different understanding of the temporality of dao. Second, based on an etymological study of the origins of the Chinese word "heng" and its philosophical use in the Laozi, I shall claim that heng explores the temporality of Laozi's dao as heng dao. Unlike chang, which asks more for constant extension, and invariable and non-changeable movement, heng in Laozi's heng dao focuses more on "living longer" of the myriad creatures, and on the concept of "never dying" of dao as a natural way of giving birth. Third, in light of this understanding of Laozi's heng dao and comparison with Heidegger's preliminary thinking of temporality of Dasein as anticipatory resolute "being-towards-death" in Being and Time, I would like to argue that Laozi's philosophy of dao is grounded on "coming-from-birth." Thus, it is life-oriented rather than death-oriented. Because of this, I propose that Laozi's heng dao as temporality of dao implies the concepts of "other-ness" and of "yielding," which lead to "co-living longer" of human beings and "co-existence" between human beings and nature.