This paper reports on a series of qualitative interviews conducted as an exploratory research effort to understand the motivations behind knowledge workers? usage of mobile digital calendars. Other findings reported on are general complaints related to the design and usage of mobile digital calendars. Semi-structured interviews were conducted with fifteen professionals who are regular users of mobile digital calendars, and have been using their system of choice for more than one year. The respondents were categorized into three categories characterized by their motivations for use and usage styles. These categories serve to better explain the reasons to use mobile digital calendars.