  The evident contrast between the time symmetry of fundamental microscopic
laws and the time asymmetry of macroscopic processes is a challenging physical
problem. The observation of unitary evolution of a general physical system by
an idealized observer whose recording and processing information is time
neutral is studied in a full information context. In the macroscopic limit, a
contradiction between observations and predictions done at different times
appears. It implies that the observer cannot read records performed at times
when the entropy of the system is larger.
