  An ensemble of quantum dot excitons may be used for coherent information
manipulation. Due to the ensemble inhomogeneity any optical information
retrieval occurs in form of a photon echo. We show that the inhomogeneity can
lead to a significant deviation from the conventional echo timing sequence.
Variation of the area of the initial rotation pulse, which generates excitons
in a dot sub-ensemble only, reveals this complex picture of photon echo
formation. We observe a retarded echo for {\pi}/2 pulses, while for 3{\pi}/2
the echo is advanced in time as evidenced through monitoring the Rabi
oscillations in the time-resolved photon echo amplitude from (In,Ga)As/GaAs
self-assembled quantum dot structures and confirmed by detailed calculations.
