  The mysterious phenomena of revivals in linear dispersive periodic equations
was discovered first experimentally in optics in the 19th century, then
rediscovered several times by theoretical and experimental investigations.
While the term has been used systematically and consistently by many authors,
there is no consensus on a rigorous definition. In this paper, we describe
revivals modulo a regularity condition in a large class of Schr\"odinger's
equations with complex bounded potentials. As we show, at rational times the
solution is given explicitly by finite linear combinations of translations and
dilations of the initial datum, plus an additional continuous term.
