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A month (masculine, etymologically related to the moon ) is a unit of time and part of a year .


Depending on the definition , a month is of different duration:

  • The period of 28, 29, 30, or 31 consecutive days . Calendars use months to keep track of time. To do this, they assign a month name to a period of one calendar month ; 12 months make up a year.
  • A month is defined in the astronomical sense as the time span of a complete orbit of a natural satellite (Trabant). In a narrower sense, “month” only refers to the earth's moon : the lunar month lasts between almost 27⅓ and a good 29½ days, depending on the definition.
The category: Month gives an overview of many uses
  • In private law in Germany, one month is the period from day x to day x of the following month. If this does not have a day x , the period ends on the last day of this month ( Section 188 (2) and (3 ) BGB ).
  • Analogous to the female period, a month of pregnancy denotes the span of 4 weeks . In some alternative calendar systems, 13 such week months make a year.
  • In banking, a booking month or billing month always lasts 30 days, a banking year therefore only lasts 360 days.

The unit symbol is M or mon.

The term "month" is used to denote time periods in the calendar system:

She was six months pregnant (time span ).

Calendar calculation basics

Monthly division of a Chinese sky disc, astronomical cycle with 28 divisions

Lunations - or their mean value, the synodic month - based on the same phases of the earth's moon formed the basic building blocks of the first calendars, which were lunar or lunar calendars , and were later partially developed into lunisolar calendars . Such calendars are still in use today in much of the world, and the Jewish calendar , the Islamic calendar and the traditional Chinese calendar , for example , continue to refer to a phase cycle of the moon as a month.

However, there is an innumerable number of lunar months in the time of a solar year , so that the length of the months had to be adjusted accordingly when a solar or solar calendar was introduced . Such a link between the length of the year and the duration of the earth's orbit around the sun and the associated separation of the months from the course of the moon first occurred in ancient Egypt in 238 BC. And was founded by Julius Caesar in 46 BC. BC also adopted for the Roman Republic (with which these years would actually be meaningful epochs for the time calculation of the Julian-Gregorian calendar).

In addition to this Julian calendar and the Gregorian calendar that replaces it and which is everyday for most people today, there are also some other solar calendars in use, in which a (calendar) month is defined as a certain part of the solar year with a fixed number of days, for example the Greek Orthodox calendar , the Coptic calendar , the Zoroastrian calendar , the Iranian calendar , the Malayalam calendar as well as various South Asian calendars.

Since 12 lunar phases last about 354 days, making this Earth's lunar year shorter than a solar year, many lunar calendars add an additional month at regular intervals. The details vary between the calendars, e.g. 7 such leap months are spread over a period of 19 years according to the Meton cycle . In any case, they occur more frequently than leap days in solar calendars . In the Julian and Gregorian calendars, February is sometimes referred to as the "leap month" in leap years .

Today, the term "month" in the Gregorian calendar only refers to fixed annual periods, the length of which differs more or less from that of a lunar cycle .

Month names

Since the Julian-Gregorian calendar from the Roman Empire was adopted in German-speaking countries, the month names used today are also of Latin origin, and most of them can be traced back to the ancient Roman calendar .

There have been various attempts to introduce their own month names, in the German-speaking area, for example, by Charlemagne in the 8th century, and again by the German Language Association in the 1920s. However, these terms could not hold up and are now only reflected in poetry ( happy month of May , spring is here , etc.). The names of the months in the French revolutionary calendar , which, like the German names of the months, were based on natural phenomena and seasons, could not establish themselves either.

  • January : ( Hartung, Eismond , in Austrian this month is only called January , less often in the southern German-speaking area)
    Named after Janus , the protector of the city gates, god of the exit and entrance, figuratively speaking of the beginning and the end, represented with two faces, looks in two directions, namely forwards and backwards. Latin ianua "threshold" (to the new year).
  • February : ( Hornung, Schmelzmond, Taumond, Narrenmond, Rebmond, Hintester , Austrian also Feber , Swiss also Horner )
    The purification or atonement month, because at the end of the year the feast of February was carried out to purify the living and the atonement of the dead (lat. February "clean").
  • March : ( Lenzing, Lenzmond )
    Named after Mars , the god of war and vegetation. In the ancient Roman calendar , the year began with March, resulting in the shift of the numerical months September to December and February as the end of the year. Since 153 BC In Rome, the consuls elected for one year took office on January 1st, which soon became naturalized as the beginning of the year.
  • April : ( Launing, Easter moon )
    Derived from the Latin aperire "open", the month of opening or blossoming.
  • May : ( Winnemond (willow month: today merry month reinterpreted, even Wonnemond ), flower moon )
    after the Roman goddess Maia named.
  • June : ( Brachet, Brachmond )
    Named after Juno , a Roman deity to whom most of the properties of the Greek queen Hera were conferred.
  • July : ( hay, hay, hay moon )
    Originally Quintilis , the "fifth month". Month of birth of Caesar (Gaius Julius Caesar). After him, this month has been since 44 BC. Chr. Julius called.
  • August : ( Ernting, Erntemond, Bisemond )
    This was originally the sixth month, accordingly called Sextilis , of the old Roman calendar. It was named in honor of the first Roman emperor Augustus in 8 BC. Renamed Augustus. 21 years later, in AD 14, August became the month of his namesake's death. (The order of the events seems strange, but at least the last year is safe.)
  • September : ( Scheiding, autumn moon )
    The seventh month (Latin septem = "seven") in the Roman calendar. From this and the following month names you can see that the counting originally started in March. It should be named after the emperor Tiberius .
  • October : ( Gilbhart, Gilbhard, Weinmond )
    The eighth month (lat. Octo = "eight") according to the Roman calendar. Here, too, the name Domitianus could not establish itself .
  • November : ( Nebelung, Nebelmond, Windmond, Wintermond )
    The ninth month (Latin novem = "nine") according to the Roman calendar.
  • December : ( Julmond, Heilmond, Christmond, Dustermond )
    The tenth month (Latin decem = "ten") according to the Roman calendar.

Astronomical Definitions

The month as the period of the earth's moon on its orbit around the earth .

The length of time from one new moon to the next. The lunation is the actual occasion for the concept of the month.
Due to the complicated movement of the moon, it fluctuates between 29 days 6.5 hours and 29 days 20 hours.

The following astronomical months describe mean values , which are therefore related to a standard epoch (currently usually J2000.0 ):

Synodic month
The time to regain equal elongation of the moon to the sun , the mean value of the lunations.
Duration 2000.0: 29.53 days = 29d 12h 44min 3s
Sidereal month
The time for one orbit of the moon around the earth in relation to a fixed direction in space, that is a complete orbit relative to a fixed star .
Duration 2000.0: 27.322 days = 27d 7h 43min 12s
Tropical month
The time for one revolution in relation to the spring equinox . It also refers to the equator and is the cycle of the declination of the moon.
Duration: Due to the precession drift of the vernal equinox, it is about 7 s shorter than the sidereal month.
Draconite Month
The period of two passes through the same lunar node . It is related to the cycle of solar and lunar eclipses ( Saros period ).
Duration 2000.0: 27.21222 days = 27d 5h 5min 36s
Anomalous month
The time between two successive perigee passages of the moon, i.e. from one point closest to the earth. The anomalous month describes the actual orbit period of the moon.
Duration 2000.0: 27.55455 days = 27d 13h 18min 33s

In astronomy , the time span between two repetitions of an event that is related to the orbit of any moon around its planet , i.e. each complete orbit, is generally referred to as a month . In this respect, the term “month” is synonymous with the orbit period .

In the solar system , these periods of time last from just a few hours to several earth years, depending on the moon.

Short forms

If used frequently or if space is limited, the month names are either shortened to three to four letters or, like the day and year, are written as digits, earlier often also in large or small Roman numerals to differentiate. In the case of variants with three initial letters for the abbreviations, the actually mandatory abbreviation point is often omitted , especially since it is not necessary for May anyway.

The national appendix to DIN ISO 8601 specifies Mar instead of Mar as the abbreviation for March in order to avoid coding problems with the umlaut. The German universal dictionary of the Duden publishing house gives abbreviations of variable length. In Austria the first month is also abbreviated Jan.

Notations of months in dates
Surname Abbr. DIN Duden number Roman
January Jan. 01 I.
February Feb February 02 II
March March March March 03 III
April Apr 04 IV, IIII
May May 05 V
June Jun. June 06 VI
July Jul. July 07 VII
August Aug 08 VIII
September Sep Sept 09 IX
October Oct 10 X
November Nov 11 XI
December Dec 12 XII


See also

Wiktionary: Month  - explanations of meanings, word origins, synonyms, translations
Wikiquote: Month  - Quotes