Calendar Systems

Converts one day between sixteen calendars in both directions (Gregorian, Julian, Roman, Hebrew, Islamic Umm al-Qura and tabular, Persian, Coptic, Ethiopian, Indian National, Chinese, Korean, Japanese era, Buddhist, Minguo and Maya) and eight Masonic eras, with day counts and the yearly ritual cycles. Hebrew and tabular Islamic dates follow the rules in Reingold and Dershowitz’s Calendrical Calculations; the Gregorian calendar was decreed by Gregory XIII’s bull Inter gravissimas (1582).

• Edward M. Reingold and Nachum Dershowitz, Calendrical Calculations, 4th ed. (Cambridge University Press, 2018)
• Gregory XIII, bull Inter gravissimas (1582)
• Daniel Sickels, The General Ahiman Rezon and Freemason’s Guide (New York, 1868)