  Using direct numerical simulations of three-dimensional magnetohydrodynamic
(MHD) turbulence the spatio-temporal behavior of magnetic field fluctuations is
analyzed. Cases with relatively small, medium and large values of a mean
background magnetic field are considered. The (wavenumber) scale dependent time
correlation function is directly computed for different simulations, varying
the mean magnetic field value. From this correlation function the time
decorrelation is computed and compared with different theoretical times,
namely, the local non-linear time, the random sweeping time, and the Alfv\'enic
time, the latter being a wave effect. It is observed that time decorrelations
are dominated by sweeping effects, and only at large values of the mean
magnetic field and for wave vectors mainly aligned with this field time
decorrelations are controlled by Alfv\'enic effects.
