Detached binary systems are subjected to a variety of physical mechanisms which are able to change their period in a continuous way and in broad band of timescales. Assuming that these changes should be detectable in O-C diagrams in a way specified by the physical theory of the underlying mechanisms, we carry out a preliminary study in a properly selected sample of detached binaries, where mass transfer is expected to lack. We primarily interested to find traces of tidal moments in observed orbital period changes (possibly coupled with stellar wind angular momentum losses). We focus our attempts on a sample of binaries consisted of late-type components where magnetic braking is expected to play a crucial role in the observed period variation rates. Theoretical and observed values are compared and possible deviations are discussed.