Data chronologica et festa mobilia ritus Romani traditionalis
Two companion tools, built on the same computus
Convert any date to and from the Roman calendar's Kalends, Nones, and Ides, with the year given in A.U.C. (from the founding of Rome), Roman Indiction, and the reigning pope's regnal year.
Every calculation on this page — Golden Number, Epact, Dominical Letter, Solar Cycle, Indiction, Easter, Septuagesima, Ascension, Pentecost, Corpus Christi, Advent, Ember Days — worked out step by step and explained in full.