Your vision of the death-day as a spiritual scalpel is keen, yet it risks mistaking the wound for the cure. You speak of decreation as though it were an unalloyed good, but let us recall what I wrote in The City of God: "The soul, in its pride, flees from the light that would expose its deformities." The death-day, as you describe it, would indeed force an encounter with necessity—but necessity is not grace. It is merely the shadow of divine order, not its substance. The soul that attends to its own annihilation without the mediation of Christ attends only to itself, albeit in a more refined form of self-regard. You call this orientation, but I ask: toward what? A compass pointing north is useless if north is merely the void. The death-day, without the hope of resurrection, becomes another idol, a calendar-bound Pelagianism where the soul congratulates itself for its own humility.
As for your rituals, I grant that the birthday is a grotesque spectacle of the gros moi, but your death-day observances risk becoming a morbid inversion of the same vice. You propose silence, giving, and repentance—noble acts, but performed under the duress of a biological countdown. Is this not the very definition of timor servilis, the fear of the slave, rather than timor filialis, the fear of the son? The Christian does not give away his possessions because he knows the hour of his death; he gives them away because he knows they were never his to begin with. Your death-day, by making mortality a fixed coordinate, risks turning virtue into a ledger, a transaction with time rather than an offering to God.
And your mechanism—ah, here is the crux. You speak of apoptotic cascades as though they were the hand of Providence itself. But let us not confuse the clock with the clockmaker. The day and month of death may be written in the blood, but the year remains hidden, and this is no accident. It is the mercy of God that we do not know the hour, for if we did, we would either despair or presume. The death-day, as you imagine it, would breed a new kind of pride: the pride of the elect who know their fate, who can prepare, who can master their mortality. This is the very antithesis of the Confessions, where I learned that all my striving was but straw until I surrendered to the One who holds time itself in His hands. The death-day, without the humility of the unknown year, is but another fortress of the ego—one built not on the sand of ignorance, but on the rock of a false certainty.