ORDO is a mobile application designed to provide information about Catholic feasts for the traditional Latin Mass. It follows the calendar established by the motu proprio of July 25, 1960.

The app displays the feasts of each day, including Sundays, vigils, octaves, ferias, and solemnities, along with their respective characteristics. In addition to the universal Church calendar, users can choose to view feasts specific to France, Switzerland, and certain dioceses.

Each day, the app provides the readings (Epistle, Gospel, and other readings) as well as the lives of saints according to the liturgical calendar, and notes on certain feasts. This comprehensive information allows users to stay connected to the rich traditions of the Catholic Church and to plan their devotions accordingly.