Internet Sources

• Books of Hours 1400-1530: Website by Erik Drigsdahl (Center for Håndskriftstudier i Danmark) on medieval books of hours in Danish and other collections with links to numerous calendar images.
• The Calculation of Easter: Website on the history and calculation of Easter by Holger Oertel.
• Calculation of the Ecclesiastical Calendar: Website on the ecclesiastical calendar by Marcos J. Montes.
• Calendar & Easter Topics: Website by G.M. Arts on the history and calculation of Easter.
• Détermination de la date de Paques: Website on the calculation of Easter by F. Lévy from the Bureau des longitudes.
• Easter Date Algorithms: Website by Henk Reints on various Easter date algorithms.
• Easter Dating Method: Website by Ronald W. Mallen on the history and calculation of Easter.
• Historical Ecclesiastical Calendar: Website on the history of the ecclesiastical calendar (with a very useful calendar applet) by Karl T. Hagen.
• Kalender – Computus: Website by Herbert Metz on the history and calculation of Easter.
• Moonwise: New Easter Dates: Website by William Morris listing the Easter Sunday dates from 1997 to 2105, according to the Orthodox (Julian) reckoning, the Gregorian reckoning and the Aleppo 1997 Proposal for the Calculation of Easter.
• Les textes constitutifs du calendrier grégorien: Rodolphe Audette’s website on the history of the Gregorian calendar and Easter reckoning is currently off-line. This link is a mirror of Rodolphe Audette’s website on the website of Henk Reints. A Dutch translation can be found here.

Calendar Conversion Software

• Calendar Tools: Online calculator by O. Lieberknecht gives indiction and year according to various styles.
• Computus Calendar Program: MS-DOS freeware program; includes Islamic and Jewish calendars.
• Historical Calendar of Western Europe: MS-DOS freeware program by Bernd Kratz.
• The Medieval Calendar: MS-DOS freeware program by Peter S. Baker.
• Medieval Calendar Calculator: Online calculator by Peter Binkley. Pick any year and month, with several options for style of calendar.
• Millesimo, logiciel de chronologie médiévale: MS-DOS freeware program by D. Muzerelle for converting and reconciling medieval dates, both historical and liturgical.