Answer
$t \approx 21.330$
Work Step by Step
$\left(1+\frac{0.065}{365}\right)^{365t} = 4$
$\ln\left(1+\frac{0.065}{365}\right)^{365t} = \ln4$
$365t \ln\left(1+\frac{0.065}{365}\right) = \ln4$
$365t = \frac{\ln4}{\ln\left(1+\frac{0.065}{365}\right)}$
$t = \frac{\ln 4}{365\ln\left(1+\frac{0.065}{365}\right)}$
$t\approx21.330$
