Heidegger's ontology of the self in terms of an extended, historically situated, ecstatically temporal unity suggest a different account of how episodic memory and similar autonoetic comportments, such as planning for the future, are possible. This ontology should enable us to make sense of these phenomena along the following lines: I can re-recognize my memory as my own because the self, whose mineness is involved both in the original experience and the re-experience, is already extended over both of these experiences.
Heidegger's view has two aspects, a phenomenology and a claim about "transcendental psychology". The transcendental part is the claim from the historicality chapter that the persistence of the self over time, insofar as it makes sense at all, has as the condition of its possibility the extended constancy of the self. The phenomenology is included in chapter six, especially §79 and §80, in which Heidegger explains his notion of world-time. I want to start with a brief look at the phenomenology.
In dealing with entities people articulate time either expressly (aussprechen) or through inexplicit interpretation (auslegen). Such articulation is "datable," i.e. it always lays out or points out a moment in terms of a determinate way in which Dasein is amidst entities: "now, that…" or "back then, when…". This articulation of time is a pervasive feature of our everyday concernful dealings. We say "it's cold," or put on a sweater or hunch, or shrug without saying anything, and in doing so we also mean "now, that it's cold". Besides being datable in terms of our being amidst entities, the time that we articulate is also spanned, and shareable or public. It is spanned insofar as the articulated time, the "now, that…" means something with a duration: "now, during the break, at dinner, this evening, this summer" etc. Such duration, however, does not show up as continuous and uninterrupted. "In going along through the everyday, Dasein never understands itself as unfolding along a continuous series of pure 'nows.' The time that Dasein takes for itself has holes, as it were". Finally, this datable, shared, spanned time is intelligible in terms of the "in-order-to" relations that ground in the "for-the-sake-of" and makes up the meaningfulness (Bedeutsamkeit) of the world. This is why Heidegger calls it "world-time".