A calendar is an overview of the days, weeks and months of a year. An obsolete term is year wise.

The word " calendar " comes from the Latin calendarium ( book-entry ). This was a list of kalendae, the respective first, auszurufenden ( calare " cry " ) days of the ancient months. These loans were disbursed and loan repayments and interest receivables due.

There are several different calendar systems, today is the world almost exclusively the Gregorian calendar in use.

Calendar is available in different - printed, illustrated, electronic - forms (see also calendar ).

  • 2.1 lunar calendar
  • 2.2 Solar Calendar
  • 2.3 lunisolar
  • 2.4 Other systems


Emergence of the calendar system

Knowing regularly taking place animal migration was already important for the early hunting cultures.

An awareness of seasonal and astronomical repeating events, for corresponding cycles of its environment, the man may have had a very early age. This included the change of day and night and the phases of the moon. Seasonal climate variability played in the agriculture of most regions of the world a significant role and could be perceived at the latest in the Paleolithic man. An observation of the changes of the night sky and the proper motions of the planets was also possible at this time.

Even the Tower of Jericho in the 9th millennium BC suggests the knowledge of the summer solstice back and Neolithic constructions such as Stonehenge testify to the efforts of the sedentary population, the natural length of the year and selected cyclically recurring celestial events such as solstice and day and be able to determine night are equally accurate. Just for agriculture was important, independent of the specific weather conditions determine the times for sowing and harvesting to make. Connected to the systematic observation of the sky were religious fertility cults - supported by the hope of a favorable return of fertility conditions. For certain agricultural dates were bound to festivals, which in turn were linked to celestial events.

For the transition from hunting to farming cultures in the Neolithic (New Stone Age ), a change calendrical notions of the moon is believed to the solar calendar. This Stone Age calendar, also Neolithic Calendars ( by Alexander Thom also called megalithic calendar) probably contains the oldest calendrical notions of humanity and is the basis of subsequent calendar variants. Analogous to the concept of the Neolithic Revolution ( the transition to agriculture ) is also spoken by the Neolithic Revolution Calendar.

The oldest still known calendar date from the early civilizations of Egypt and Mesopotamia. Here were already two basic types of calendars that characterize most calendar systems today: the oriented at the moon phases lunar calendar and the astronomical calendar that reflects the course of the heavenly bodies.

At the latest by the Babylonians of the seven -day weekly cycle has been developed, which regulates the flow of everyday life almost worldwide today. In other calendars were similar cycles, between five and ten days.

The adaptation of weeks and months to follow the fixed size of the astronomical year was not easy to solve. It came to the formation of different calendar systems.

Observation Calendar

Early calendar systems were obtained by observation ( astronomical calendar). With the occurrence of certain defined sky event (eg, the new moon, or of the day and night are equally long in the spring ) began a new cycle. They had to be readjusted regularly.

This method had a major drawback: In large rule spaces an event at different locations could not be perceived at different times so that different data were counted. If, however, the occurrence of an event only at a specific location (eg capital or the main temple ) was instrumental, then far -lying areas could often be taught only after days of it. There were such problems, for example in the former Jewish calendar, where the high priest decided on the first sighting of the crescent new moon. The long lines of communication, it could happen that a religious festival in remote areas has been celebrated on the "wrong" day. Also, it was not possible to predict short end of the month, which date would be in seven days, for example, because the new moon was not predicted, but determined by daily observation.

More and more cultures began to calculate their calendar. The last serious attempt to establish a monitoring calendar, was made in the French Revolution ( French Revolutionary Calendar ).


The calculation of calendars ( calendar arithmetic ) requires extensive astronomical and mathematical knowledge. In the development of the early Egyptian astral Sothiskalenders this knowledge were available. The introduction of an Egyptian administrative calendar on 365 -day basis was followed by no later than the third millennium BC However, this could not prevent the wandering through the seasons. The Egyptian kings complained about the season shift, but only Ptolemy III. undertook 238 BC an attempt to introduce a leap day. After his death, the ancient Egyptian calendar management was used alongside the new leap day calendar but again. The Julian calendar, which was introduced in 45 BC by Julius Caesar, based nevertheless on the Calendar form of Ptolemy III.


Both lunar and solar calendar must operate with switching days or different month lengths which are inserted after a specified mathematical rule in the normal course calendar. A solar calendar usually requires an extra day approximately every four years ( in the Gregorian calendar, this is February 29 ) to adjust the average daily number of the length of the solar year. A lunar calendar has the month lengths between 29 and 30 days vary, because the time between two equal phases of the moon takes an average of approximately 29.531 days.

The insertion of an additional day, month or year in a calendar system is called embolism ( ancient Greek ἐμβάλλειν " on") referred.

Calendar systems

→ Main article calendar systems

Moon Calendar

Lunar or lunar calendar based on the moon phases. The German word month is derived etymologically from the moon. However, the month of the Gregorian calendar has except the name nothing to do with the lunar cycle, as it takes almost a day longer with an average length of 30.437 days than the average synodic month.

The disadvantage of a pure lunar calendar is that it can not correspond to the solar year, a property that is in subtropical and tropical latitudes, often has the meaning which it has in -dependent of the seasons cultures. So take in the famous still used lunar calendar, the Islamic calendar, the year with 12 months on average 354.372 days. The Islamic months "walk" year after year by about eleven days in the Gregorian calendar forward. Even the date of Easter follows a lunar calendar (see: Computus ( Easter calculation ) )

Solar Calendar

Most cultures were based on their timing at particular seasons by the sun ( solar or solar calendar ). Accordingly, the basic type of solar calendar has produced the most variants. The solar year is based on the tropical year, which related to the vernal equinox orbit of the earth around the sun. This is the starting point for the general one-year term.

The now globally widespread Gregorian calendar is a solar calendar.


The lunisolar calendar is an attempt to adapt a pure lunar calendar to the solar year. Since the length of the months is determined by the phases of the moon, no leap days can be inserted as the solar calendar. The solution lies in the insertion of leap months. Therefore, the length of the lunisolar calendar years fluctuates between about 353 and about 385 days. Known lunisolar are the Jewish, the traditional Chinese and the Celtic calendar.

Other systems

There are only a few calendar systems are known which neither oriented to the sun by the moon. The astronomical Egyptian calendar was based on the very bright star Sirius. The Mayan calendar was based on a regular sequence of 20 days and of a 52 -year Calendar Round.