When Da-sein is being ahead of itself in such a way that it is being towards its ownmost possibility - which is death - the possibility of being free for authentic existentiell possibilities is opened up. The anticipation of death provides a resoluteness that drives off every trivial possibility; this resoluteness that exists in the moment – rather than some kind of isolated present – is Da-sein’s ability to be free for authentic existentiell possibilities, as opposed to the possibilities that Da-sein just finds lying around in the public realm.
Attunement and falling prey, as temporal, correspond to having-been and making-present. Attunement can either be retrieve, or forgotteness, which is the vulgar past. Falling prey temporalizes as making-present or the Moment, and understanding temporalizes as awaiting or anticipation, corresponding to the vulgar future. The three are a unity; they interpenetrate each other as an ecstatic unity. For example, attunement temporalizes as the “past,” but still temporalizes itself as a future that makes present.
The anticipation of death and the resolute projection upon authentic existentiell possibilities is known as anticipatory resoluteness. This is how Heidegger brings together the ontic and the ontological, the existential and the existentiell, authentic temporality meeting authentic possibilities. I’ve heard it argued that this is analogous to Kant’s schematism, in which Kant brings together intuition and the categories.
Since the possibility of Da-sein’s being-a-whole lies in anticipatory resoluteness, this resoluteness must have a temporal structure. It is being towards Da-sein’s ownmost possibility. This is a coming-toward-itself which is the “primordial phenomena of the future.” This is not a point that could be described as somehow spatially distant, or a potential that is “not yet” actual, but rather Da-sein’s ability to come towards itself. (BT 299)
Anticipatory resoluteness also understands Da-sein as guilty, as being thrown and not mastering its ground. This is what will be known vulgarly as the past. Da-sein, understanding itself as thrown, is how Da-sein can be “in the way that it already always was.” This is Da-sein’s “having been.” There is a unity here with coming-towards; only because Da-sein has been can it come towards itself futurally – “authentically futural, Da-sein is authentically having-been.” (BT 299) By anticipating death, we see ourselves as already having been and able to act in the moment.
I’m going to go over one more topic and make 2 points about it – vulgar time, which is basically the linear time of common sense that we all know and love. The origin of vulgar time lies in Da-sein’s average, everyday inauthenticity. The common concepts of future, present and past represent genuine phenomena, but it is a derivative one. Because temporality is not an aggregate of nows, these nows cannot be said to stretch into infinity. If time is finite, then what do we do with the time that apparently continues? Heidegger is not denying that “time goes on,” he is saying that the belief in a time that moves out of the indefinite past and into the indefinite future is the result of a vulgar notion of time. Commonly, time is seen as infinite, but this conception is really only possible on the basis of temporalizing finitude. (BT 304)
In section 66, Heidegger lays the ground of what will become the datability of time. In an average, everyday way, care is about taking care of things. When using things, Da-sein uses time. In other to use time, it must be datable and calculable. (BT 306) In this way, innerworldly beings are encountered in time; their temporal quality is “within-timeness.” There is a critique of Bergson here that I’ll just mention – this within-timeness is an actual phenomena, not an externalization of a qualitative time into space. I have nothing to say about that, but someone else might.
For Heidegger, all datable time is public time and lies on top of primordial temporality. The public “orients” itself towards this time, “so that it must somehow be available for everyone.” (BT 378) Time can be taken care of in terms of events and innworldly beings, but this occurs in a horizon of “time-reckoning,” which always involves astronomical and calendrical time. The essence of taking care of time is not about measuring quantities or assigning numbers to periods of time. Measured time arises because of thrownness; primordially, temporality is Da-sein reckoning with time. (BT 378)
Public time always presupposes the structure of “then” and “when.” When the term ends, it is time to hand in essays. This public “then” is the structure of significance, which is part of understanding and interpretation, so “it constitutes the worldliness of the world.” (BT 380) This “time for” is what Heidegger will call world time. World time is not an inner worldly being, of course, but rather the condition of such. World time is presupposed when we use clocks, when we calculate and measure time. By saying what I’ve said, I’ve tried to point out how there is an authentic temporality that underlies our common notions of time, and all our calculation of it.
By way of conclusion, I’ve tried to summarize how both Da-sein’s a priori, existential structures and datable public time become meaningful and intelligible only on the basis of an underlying, unifying temporality.