Abstract In the context of information theory, Shannon's entropy plays an important role. Since this entropy is not applicable to a system that has survived for some units of time, the concept of residual entropy has been developed in the literature. This definition deals with random variable truncated above some t, i.e. the support of the random variable is taken to be ( 0 , t ). In this paper, some ordering and aging properties have been defined in terms of generalized past entropy and their properties have been studied. Quite a few results available in the literature have been generalized. The uniform distribution has been characterized through the generalized past entropy.