  Let $S(t) \;:=\; \frac{\displaystyle 1}{\displaystyle \pi}\arg
\zeta(\frac{1}{2} + it)$. We prove that, for $T^{\,27/82+\varepsilon} \le H \le
T$, we have $$ {\rm mes}\Bigl\{t\in [T, T+H]\;:\; S(t)>0\Bigr\} = \frac{H}{2} +
O\left(\frac{H\log_3T}{\varepsilon\sqrt{\log_2T}}\right), $$ where the
$O$-constant is absolute. A similar formula holds for the measure of the set
with $S(t)<0$, where $\log_kT = \log(\log_{k-1}T)$. This result is derived from
an asymptotic formula for the distribution of values of $S(t)$, which is
uniform in the relevant parameters, and this is of crucial importance. This in
fact depends on the distribution of values of the Dirichlet polynomial which
approximates $S(t)$, namely ($p$ denotes primes)
$$V_{y}(t)\,=\,\sum\limits_{p\le y}\frac{\sin{(t\log{p})}}{\sqrt{p}}.$$
