Abstract. Changes in modern work environments, combined with advances in sensing and machine intelligence, have given rise to a new class of groupware applications that seeks to facilitate workplace communication through the prediction of future availability and/or location. We present the results of a four-month deployment of an experimental predictive calendar system in an academic setting. While participants appreciated several novel features of the system, most resisted adoption due to the uncertainty of its predictions, its effects on privacy and impression management, and accessibility issues. We present implications for designers who seek to incorporate forecasting components into their groupware tools using observations from the study.