Table of Contents

• Introduction
• Lunisolar cycles
• Old Roman Calendar
• Julian calendar
• The Council of Nicaea in 325
• The Roman Dating System
• Calendar eras
• Different beginnings for the new year
• The Martyrology
• Dies caniculares
• Dies egyptiaci
• Gregorian calendar reform
• Reception of the Gregorian Calendar
• When Easter is celebrated
• Calculation of Easter Sunday in the Julian calendar
• Calculation of Orthodox Easter Sunday in the Julian calendar
• Calculation of Easter Sunday in the Gregorian calendar
• Calculation of Easter Sunday online
• Calendarium gregorianum
• Table of dates for the Easter holidays
• Distribution of Easter Sundays in the Gregorian Calendar
• Graph distribution of Easter Sunday depending on the epact
• The difference between Easter Sunday in the Julian and Gregorian calendars
• The Easter Paradox
• Chronological Cycles
• Golden number
• Epacts
• Solar cycle
• Dominical letter
• Indiction
• Gaussian algorithm for calculating Easter Sunday
• Carter's algorithm for calculating Easter Sunday
• Tabula Paschalis Nova Reformata
• Tabula Noviluniorum
• French Republican calendar

Indiction

Long before it was customary to count years according to their year, “indictions,” most often expressed in Roman numerals, were used. The indiction is a number indicating how many times a given year appears in the order of a fifteen-year long, constantly recurring cycle. Therefore, knowledge of the indiction alone is not enough to accurately determine the year. For example, if the document is dated as Indiction 13, we do not know whether it is the year 1000, 1015, etc. To determine the exact year, it is necessary to know more data, such as who ruled, when did they live, and the like. The origin of the indiction is uncertain, but one possible explanation is that it was introduced to commemorate the victory of the Roman emperor Constantine at the Battle of Milvian Bridge in 312. The following year, the indicator was equal to 1, and Roman rulers then set tax collection schedules in accordance with the indiction. Another theory about the origin of the indiction attributes it to Egypt at the end of the third century. What originally had been a five-year long re-assessment period for tax collection was switched to fifteen years around this time. There are several many other types of indictions, but the most widely used were:

• The Greek, or Byzantine, indiction (indictio Graeca, indictio Constantinopolitana) began at the same time as the Byzantine year on the 1st of September (just before our current-day 1 January). From Byzantium it spread into southern Italy and Sicily. According to it, the papal office dated only from the end of the 5th century. It was not until the 12th century that other types of indictions appeared in addition to the Greek one.
• The indiction Bedova (incorrectly called imperial) begins on 24 September, just before our 1 January. The exact origin is unknown, but perhaps it was invented by Beda the Venerable himself. Its spread was not solely confined to England, but can also be found throuhgout Western Europe. In some periods it even found use in the papal office.
• The Roman indiction (indictio Romana, indictio pontificia), sometimes also called New Year's indiction, began on either 25 December or 1 January. It was probably created in an effort to reconcile the indiction year with the calendar year. As a result, it found extremely widespread use in the Western world. According to it, and Dionysius Exiguus himself, it was commonly used in the 7th century Rome, with even though the papal office of the time recording its years according to the Greek indiction.

Only integers are counted, the '%' character (the modulo) indicates that the remainder from the division is the only part to be used.

Below is a table of indiction values ​​from the year 0 (according to astronomical years) to the year 5999. It is easy to use, simply find the century in the column and the year of the century in the row. The desired value will be at the intersection. For example, if we are interested in the value of the indiction for the year 1348, we would locate column 1300 and then row 48, and at their intersection is the number 1, which gives us the indiction for the year 1348.