Information dissemination dynamics is an important performance index for characterizing the speed and scope of information dissemination in a network. Several analytical models have been proposed to estimate the information dissemination dynamics for social networks adopting a susceptible-infected information propagation model and having a constant informed rate. This letter extends existing model to analyze the social networks adopting either a susceptible-infected or an independentcascade information propagation model and having a timevarying informed rate. Validated by simulations, our model demonstrates its flexibility and applicability to approximate the complicated propagation behaviors of advertisement-like or malware-like information.