  The availability of about a decade of uninterrupted sky monitoring by the
Fermi satellite has made possible to study long-term quasi-periodicities for
high-energy sources. It is therefore not a surprise that for several blazars in
the recent literature claims for such periodicities, with various level of
confidence, have been reported. The confirmation of these findings could be of
tremendous importance for the physical description of this category of sources
and have consequences for the gravitational wave background interpretation. In
this work we carry out a temporal analysis of the Fermi light curves for
several of the sources mentioned in recent literature by means of a homogeneous
procedure and find that, globally, no strong cases for blazar year-long
quasi-periodicities can be confirmed. The computed power spectral densities are
all essentially consistent with being generated by red-noise only. We further
discuss the meaning and the limitations of the present analysis.
