Answer
$3.9\times 10^7years$
Work Step by Step
First of all, we find the frequency
$f=\frac{f_{B-flat}}{2^{59}}=(\frac{466.2}{2^{59}})=8.087\times 10^{-16}Hz$
Now we can calculate the time period as
$T=\frac{1}{f}=\frac{1}{8.087\times 10^{-16}}=1.237\times 10^{15}s$
We convert this time into years
$T=1.237\times 10^{15}(\frac{1yr}{3.16\times 10^7})=3.9\times 10^7years$