  Under the assumption of an initial datum divergence free and in L2, we prove
the existence of a weak solution to the Navier-Stokes initial boundary value
problem enjoying the energy equality on (0,t), almost everywhere in t>0, in
particular, for all t $\in [\theta, \infty)$, with $\theta := \theta(||v0||2)$.
Also, the result allows us to refine some others.
