Can Immortality Be Proved?

According to The Speculist:

By the most literal definition, immortality would be impossible to achieve or prove. Even somebody who lives 25 quintillion years isn't immortal -- they just haven't died yet. The only way to ever establish that anyone is immortal is to go all the way to the end of time and confirm that that individual is still alive.

If you wake up one morning and realize the year is ε₀, you're immortal.