For the entirety or remainder of one's life. until my dying day, I will never forgive him for what he's done to our family.Despite all her doctors' warnings, my grandmother smoked cigarettes like a chimney until her dying day.See also: dying, until
till/to/until your ˌdying ˈday
for as long as you live: I swear I won’t forgive her to my dying day!See also: dying, till, until