Kalendarium is an unfunded, international project begun at Penn to build a crowd-sourced tool for collecting and identifying all the world’s medieval liturgical calendars. The project includes participants from the University of Pennsylvania, Stanford University, the Morgan Library, Radboud University Nijmegen, the University of Antwerp, and the University of St. Andrews in Scotland. From calendar to calendar, the saints and feasts celebrated — especially minor and local saints — differ with the place of a calendar’s intended use. Kalendarium will make easy the task of entering each of a calendar’s celebrations and, once its database of calendar information has grown sufficiently large, adapt to user entry by suggesting the likeliest saints for a given calendar. To date the Kalendarium team have developed prototype “proof-of-concept” applications to demonstrate project ideas and is now in the process of amassing the large database of saints and feasts needed for daily identification of saints.