The mobile Internet is one of the most promising application domains in the computer communications. The mobile handsets close the gap between end users and the computer communications using the 24-hour 365-day availability. The emerging success in Japan has demonstrated the potential capabilities for the next generation Internet platform. The close relationship to the end user reveals a new research area of the user behavior analysis. Using the user transaction logs for over a year, the author tries to build up a new knowledge domain: know-when knowledge. A methodology to capture the user behavior change over a span of time is important to manage the subscription-based mobile Internet services. Using the know-when knowledge acquisition, the author explores the possible cues for the long-term analysis of user behavior patterns using the long-term transaction logs. Considering the behavior dynamism of the mobile Internet users, it is important to explore the know-when technologies for the future mobile Internet marketing.