List of all pages on this website

Printable monthly calendar

A clear and concise monthly calendar that displays all of its associated weeks and holidays.

Printable yearly calendar

A simple annual calendar suitable for printing on your printer.

Introduction

This book deals with the historical development of the Gregorian calendar.

Lunisolar cycles

Calendars from every known civilisation have fallen under the classifications of lunar, solar, and lunisolar.

Old Roman Calendar

According to legend, the Old Roman calendar was created by the founder of Rome, Romulus himself, in the year 753 BC.

Julian calendar

In order to avoid further confusion in the Roman calendar, Gaius Julius Caesar reformed the Roman calendar in 46 BC.

The Council of Nicaea in 325

The first ecclesiastical council of Nicaea occurred in 325, in what is now known as the Turkish town of Iznik.

The Roman Dating System

The Romans counted the days of each month in a somewhat confusing manner.

Calendar eras

An era is a continuous series of years measured by the occurrence of a significant event, whether legendary or historical. The earliest days of an era are called the epoch.

Different beginnings for the new year

On this page you can find six of the most commonly used starting dates that have been in use throughout Europe.

The Martyrology

The martyrology was originally designed as a calendar that listed all of the recognized saints in Roman Catholicism.

Dies caniculares

The ancient Greeks and Romans noticed the temperature was at its peak during the months of July and August, and coincidentally, this period of time also saw the beginning of the heliacal rising of Sirius.

Dies egyptiaci

The Dies egyptiaci, egyptiacus, aeger, mali. It was considered a sign of the “unfortunate days”, when it wasn’t appropriate to work, trade, or travel.

Gregorian calendar reform

The most widely used calendar the world over is the Gregorian calendar.

Reception of the Gregorian Calendar

The correction of the calendar in its original state was initially adopted in 1582, but only by Roman Catholic countries.

When Easter is celebrated

Easter Sunday falls on the first Sunday after the Paschal (ecclesiastical full moon), which being fixed as 21 March, makes Easter Sunday capable of occurring as early as 22 March and no later than 25 April.

Calculation of Easter Sunday in the Julian calendar

Detailed description of the calculation of Easter Sunday in the Julian calendar.

Calculation of Orthodox Easter Sunday in the Julian calendar

Detailed description of the calculation of Orthodox Easter Sunday in the Julian calendar.

Calculation of Easter Sunday in the Gregorian calendar

Detailed description of the calculation of Easter Sunday in the Gregorian calendar.

Calculation of Easter Sunday online

An online calculation of Easter Sunday in the Gregorian calendar.

Calendarium gregorianum

This table shows a medieval chronological aid, published in the book Explicatio, under the title of CALENDARIUM GREGORIANUM.

Table of dates for the Easter holidays

A table of calendar dates in the Gregorian calendar for the most important Easter holidays in the Eastern and Western churches.

Distribution of Easter Sundays in the Gregorian Calendar for the years 1800-2299

In this table you will find the occurrences of Easter Sunday on given dates for the next few centuries

Graph distribution of Easter Sunday depending on the epact

We can make a graph that displays every possible calendar date for Easter Sunday, along with the corresponding Gregorian epact in which each occurs.

The difference between Easter Sunday in the Julian and Gregorian calendars

The distribution graph below shows the difference between Easter Sunday in the Julian and Gregorian calendars by the amount of weeks.

The Easter Paradox

If the predicted calculation for the first full moon of spring fails to match the observed astronomical data, the "Easter paradox" occurs.

Chronological Cycles

Chronological signs, characteristic marks, and other unique church numbers found in old calendars, are now considered obsolete.

Golden number

In this 19-year lunar cycle, 235 phases of the moon alternate nearly perfectly.

Epacts

The Gregorian epact is a necessary prerequisite for calculating Easter Sunday.

Solar cycle

This solar cycle is composed of a continuously numbered series of 28 years, where all the years that form an identical match in week order are marked.

Dominical letter

To create the list of Dominical letters, a cycle was composed of the first seven letters of the alphabet (A - G).

Indiction

The indiction is a number indicating how many times a given year appears in the order of a fifteen-year long, constantly recurring cycle.

Gaussian algorithm for calculating Easter Sunday

A reconstruction and analysis of the Gaussian algorithm for calculating Easter Sunday. An attempt to improve the algorithm.

Carter's algorithm for calculating Easter Sunday

A reconstruction and analysis of Carter's algorithm for calculating Easter Sunday.

Tabula Paschalis Nova Reformata

An easy-to-read table for quick and simple identification of Easter, and all other church holidays that derive from it.

Tabula Noviluniorum

A table of ecclesiastical new moons published by Christopher Clavius in his book NOVI CALENDARII ROMANI APOLOGIA​.

French Republican (revolutionary) calendar

The Republican (often called Revolutionary) calendar is a product of passionate opposition to the old order during the Great French Revolution.