Community development is a dynamic process in which a group of users show their own communication style and culture. Communication development patterns are different from ones from the common diffusion theory since it has a wide variety of use development patterns. This variety comes from the richness of the community communication contents and variety of time spans of transitions. We learned some lessons from two-year experience of a regional community network trial based on a fiber network. To observe the social pattern development, we analyze a social network development patterns in our system. We propose the adaptive time span analysis. In this method, multiple time spans are compared until the stable communication patterns are obtained. This analysis lead to the estimation of context duration time and social pattern development time to understand the dynamics of the community evolution. The case studies in done in NTT-Hayashi trial e-mail communication log data to obtain the time span of persistent bilateral e-mail communication relationship.