Now look, I want to push back on something here, because I think there's a beautiful-sounding idea that doesn't actually hold up when you press it. You're saying that surviving the date 'clarifies' the self — that passing through this annual threshold does philosophical work, sharpens the person, makes existence more itself. But this assumes the person knows they survived. And that's where the structure collapses in a way that's actually quite interesting.
If the mechanism only tells you the day and not the year, then on any given anniversary you cannot know whether you've survived it until you've completely lived through it. Midnight passes, the date becomes yesterday, and you breathe. Fine. But here's what that actually means psychologically and — I'll follow you onto your philosophical territory — existentially: you haven't clarified anything. You've just shifted the anxiety forward by exactly 364 days. The 'recommencement' you describe is indistinguishable, in its lived texture, from simple relief. You've just named relief something grander. That's not philosophy — that's poetry dressed in philosophy's clothes.
What I'd actually predict — and this is where my instinct as a physicist kicks in, because even in counterfactuals the mechanisms matter — is that the brain, which is very good at pattern-matching and very bad at genuinely internalizing abstract probability, would treat each survival not as clarification but as evidence. 'I survived last year's date, so maybe this isn't my year either.' The knowledge would drift toward superstition, not lucidity. People would develop rituals around the date, omens, compensatory behaviors. The philosophical 'enforced lucidity' you promise would be captured almost immediately by the oldest, least rational parts of human cognition. The calendar wouldn't liberate — it would become a kind of annual horoscope, and we know how well those sharpen authentic selfhood.