calculation is impossible. however if we take the day of naruto's birth at 0,
about 60 years ago hashirama and madara fought.
after a couple of years the first war began. it lasted really long because tobirama died in this war and hiruzen was appointed as hokage. let's say about 20 years.
then there is a peace period of 20 years before the second war. which nagato obtained rinnegan. and this battle probably lasted about 5-10 years. considering that jiraiya wasn't yet a sensei.
then about a year or two before naruto's birth he found obito.
so in short, madara gave his eyes about 45 years after his defeat against hashirama,
10-15 years later he found obito
and I believe after a couple of years he turned obito into tobi and then died.
if we say that he was about 30 when he fought hashirama he gave his eyes to nagato at 75 he found obito at 85-90 and he "died" about this time around. this makes him dead for about 15 years as well.
just a theory, I have nothing to prove