Calendar design

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Calendar drafts are calendars that were designed for political, religious, astrological, astronomical, literary or economic reasons or simply as a game of ideas and were only officially used for a short time or were only proposed to improve the generally used (mostly Gregorian ) calendar supplement or replace.

Criticism of the Gregorian calendar

The Gregorian calendar serves as the basis of the international standard ISO 8601 and is used worldwide, e.g. Sometimes, however, parallel to traditional local systems. Except for the switching rule, it corresponds to the older Julian calendar . Nevertheless, there are some historical or systematic weaknesses in relation to various areas of application, which are criticized accordingly.

  • The months are unevenly long with 28 or 29, 30 and 31 days.
  • The short and long months are irregularly distributed over the year, so that the quarters are also unevenly long.
  • Neither years , half-years, quarters nor months correspond to the seven-day weekly cycle , so that there are 14 different annual calendars (7 variants each of the common year and the leap year). Therefore, annual holidays etc. in the following year are either on a different weekday or on a different date.
  • The era , d. H. the definition of the epoch is determined by Christianity and therefore not confessionally neutral.
  • The leap years are not regularly distributed over the 400-year cycle.
  • The average year is slightly longer than the astronomical year at 365.2425 days, although there are several ways to determine it.
  • The months do not coincide with the phases of the moon.
  • In many languages, names for weekdays and months are based on outdated concepts, for example in German:
    • January , March , May and June go back to Roman deities.
    • July and August are named after Roman emperors.
    • September , October , November, and December are based on the Latin ordinal numbers 7 to 10 instead of 9 to 12, as the monthly count began earlier in March.
    • Tuesday , Thursday and Friday have their names from Germanic deities.
    • Wednesday is in the middle of the five-day work week and the Christian week beginning on Sunday, but not the civil 7-day week beginning on Monday.

Requirements for a globally applicable, culture-neutral calendar

Different demands are made of a new calendar, some of which contradict each other. Some are radical-schematic or purely aesthetic in nature, others are more conservative in order to ensure acceptance or compatibility with the previous or with religious festival calendars.

Astronomical reference
Most calendar designs are more or less based on the orbital times of the earth around the sun ( year ) and the moon around the earth ( month and week ) as well as the time for the earth to rotate around its own axis ( day ). Every design must take into account that there are no integer ratios and that they are not to be expected in the foreseeable future. A permanent correspondence of the times of solstices and equinoxes with monthly or quarterly boundaries is not possible in an arithmetic calendar due to the non-harmonic conditions of celestial mechanics . This is evident, for example, from the fact that northern summer is a few days longer than northern winter.
Harmony, aesthetics
One of the goals of most designs is to keep the number of days per week, days and weeks per month or quarter, and days, weeks, and months per year either the same or in a simple sequence.
Date-weekday correlation
In a perpetual calendar, every day-month date is on the same day of the week every year. To do this, it is necessary either to intercalate a leap week or to introduce individual days outside of the weekly cycle. The latter is particularly rejected by representatives of the Abrahamic religions, for whom the unbroken series of complete weeks is of great importance. In ancient times, leap months were intercalated in the case of larger discrepancies in numbers, often irregularly as required and of uneven length.
Weeks and months
Some religions insist on the continuation of the seven-day cycle, although 5, 6, 8 or 10 days per week have also been suggested for practical reasons. There are different views of the preferred first and last day of the week. There is also resistance to changing the number from 12 months (see zodiac sign ) to 10 or 13.
Switching rule
There are both advocates of purely arithmetic switching rules, as so-called "astronomical constants" are no longer constant for very long periods of time, as well as advocates of astronomical rules that rely on observation, especially for calendars that take into account the phases of the moon.
To make the transition to a new calendar system easier, some drafts aim to be as compatible as possible with the Gregorian calendar. This also applies to some calendars with leap weeks, which are based on ISO 8601.
The historical link between the current calendar and certain religions and cultures is widely criticized. However, changes in this regard are usually combined with others.

Comparison of some calendar designs

The Gregorian calendar is compared to the two reform calendars from the First French Republic and the Soviet Union, which have already been temporarily implemented, as well as several proposed calendar drafts based on a few criteria.

Calendar drafts (leap year figures in parentheses)
calendar Days per Days without a week Months a year Weeks per month perpetual Switching object Years per cycle Year variants
year month week
Gregorian 365 (366) 28 (29), 30, 31 7th - 12 not fixed No Day 400 14th
Leap week 364 (371) [28, 35] 7th - [12, 13] [4, 5] Yes week 400 2
French 365 (366) 30th 10 5 (6) 12 3 No Day astronomic 2
Soviet '29 365 (366) 30th 5 5 (6) 12 6th Yes Day 400 2
Soviet '31 365 (366) 30th 6th 5 (6) 12 5 Yes Day 400 2
world 365 (366) 30, 31 7th 1 (2) 12 not fixed Yes Day ? 2
Cotsworth /
365 (366) 28 7th 1 (2) 13 4th yes and no Day ? 2
Comte 365 (366) 28 7th 1 (2) 13 4th Yes Day ? 2

The weekly calendar according to ISO 8601 itself does not contain any months, but corresponds to the Gregorian calendar, but there are various suggestions to divide the 52 weeks (plus leap week) into 12 or 13 months. The information in square brackets relates to this.

See also

Web links