This paper presents an investigation about the instant in Heidegger, articulating the analytics of Dasein by Being and Time with the thought of Ereignis. Therefore, it seeks to think, as a presupposition, the existence in his character of temporality. The human being is conceived
as Dasein, i. e, in its fundamental relationship to the Being as such. The essence of Dasein is existence. The existence is grounded on Sorge (concern, care), which, in turn, is grounded on temporality. The most own temporality brings together future, past and present in the dynamics of an anticipatory decision on which the man, accepting himself as being-unto-death, it becomes free for their power-to-be authentic, in a response of dedication and self-donation to the call of
Being. This gather together future, past and present in the authentic existence, i.e, in the most own temporality: the instant.
Keywords: existence; resolution; temporality; instant; man; Being.