24 x 365 = 8760 hours in a year
8760 x 60 = 525.600 mins in a year
525.600 x 60 = 31.536.000 seconds in a year
Do the rest yourselves. I don't have a calculator with so many zeros.
31.536.000 seconds _________________ 1 year
1.000.000.000.000 (1billion) seconds ___ X years
PS: for Spain and Latin America, a billion equals 1 million of millions, that's why it takes 12 zeros.