the data explained — every ecclesiastical calculation for a Gregorian year, worked step by step, per the traditional Roman Rite
Two companion tools, built on the same computus
The year's full chronological data at a glance — Golden Number, Epact, Dominical Letter, Solar Cycle, Roman Indiction, and all the moveable feasts and Ember Days.
Convert any date to and from the Roman calendar's Kalends, Nones, and Ides, with the year given in A.U.C., Roman Indiction, and the reigning pope's regnal year.