One day lived
Is one less day to live
Days lived so far
A finite number X
Days left to live
A finite number Y
Total days of life
A finite number U
Y = U - X
Therefore tomorrow S
S = U - X - 1
S + 1 = U - X
U = S + 1 + X
Which means
Total days of life
Equals all the days lived
Plus tomorrow and next day