  A flavor-tagged time-dependent angular analysis of the decay
$B_s^{0}\rightarrow\phi\phi$ is performed using $pp$ collision data collected
by the LHCb experiment at $\sqrt{s}=13$ TeV, the center-of-mass energy of 13
TeV, corresponding to an integrated luminosity of 6 fb^{-1}. The
$\it{CP}$-violating phase and direct $\it{CP}$-violation parameter are measured
to be $\phi_{s\bar{s}s} = -0.042 \pm 0.075 \pm 0.009 $ rad and
$|\lambda|=1.004\pm 0.030 \pm 0.009 $, respectively, assuming the same values
for all polarization states of the $\phi\phi$ system. In these results, the
first uncertainties are statistical and the second systematic. These parameters
are also determined separately for each polarization state, showing no evidence
for polarization dependence. The results are combined with previous LHCb
measurements using $pp$ collisions at center-of-mass energies of 7 and 8 TeV,
yielding $\phi_{s\bar{s}s} = -0.074 \pm 0.069 $ rad and $|\lambda|=1.009 \pm
0.030$. This is the most precise study of time-dependent $\it{CP} $ violation
in a penguin-dominated $B$ meson decay. The results are consistent with
$\it{CP} $ symmetry and with the Standard Model predictions.
