Answer
$2.0s$
Work Step by Step
We know that
$\Delta t=\frac{\Delta t_{\circ}}{\sqrt{1-\frac{v^2}{c^2}}}$
We plug in the known values to obtain:
$\Delta t=\frac{1.00s}{\sqrt{1-(\frac{\frac{\sqrt3 c}{2}}{c})^2}}$
This simplifies to:
$\Delta t=2.0s$