Symmetry454
Weekly calendar are calendar years, the most important subdivision are not months, but weeks. Such calendars can be used in parallel with monthly calendars within a calendar system. In particular, the international standard ISO 8601 defines the numbering of calendar weeks indirectly, a weekly calendar.
Leap years
The ISO week calendar depends on the proleptic Gregorian calendar off by the Gregorian year, usually in 52 full weeks (364 days) is divided, in each case up to 3 days from December of the previous year on the one hand and from the January of the following year may be included on the other hand, and, if necessary - about every 5 to 6 years - a 53rd week is added (so 371 days ).
Weekly calendar that will be compatible with ISO 8601, followed by a 400 - year cycle in which there are 71 years with switching weeks, while there Gregorian leap years ( on February 29 ) are in the same period 97.
In each cycle, the ( eg, n = 5 for 2001) in a given year with the number 400 · n 1 begins, these are the years with 53 weeks, ie they begin on a Thursday and ends on a Thursday or a Friday in common years and leap years:
Switch
The years in which January 1 in the Gregorian calendar is a Monday and a switch to a compatible calendar week would therefore facilitate something, are the following:
Reactions and suggestions
Although weekly calendar can be used in principle in parallel with the usual monthly calendar and of the economy as well, there are various proposals, the months ( and quarters) to rearrange, so they usually contain a round and uniform number of complete weeks.
13 -month calendar
In a single month length of four weeks match 13 months in a normal week year of 364 days. There are several calendar designs that this fact make use of and differ in several details: You can annual 365th day and provide in leap years a 366th day, which belong to any one week, and no month and are inserted at various points in the year, or they perform, such as ISO 8601, if necessary, a switch 53 a week, which in turn belongs to different months or may be a separate, 14th month, which mostly comes at the end of the year, but can be inserted in principle between any 2 months. See some reform proposals for all months ( some also for the weekdays ) new names before, while others on the additional month (eg " Newton" ) limit, which, however, again at various points in the year - inserted - usually in the middle or at the end can be.
The former belongs to the positivist calendar, which in 1849 by Auguste Comte (hence Comte calendar) was developed. While still maintaining the traditional weekday names, he named the months and individual days in the year after famous personalities. Not least because he could not prevail in the mold. In 1923 he was converted by Moses Cotsworth the International Perpetual calendar. Cotsworth retained the traditional month names, only he called the 13th month in the middle of the year either Sol or Midi. Both calendar, in normal years, and in leap years two additional days. In Comte calendar they are as white days at the end of the year, the International Perpetual calendar the extra day is at the end of the year, the leap, however, at the end of June.
This system with uniform month length allows the statistical comparison with previous and subsequent months, but can be badly divided into quarters, so it is interesting for economic activities without large seasonal fluctuations than others.
Quarterly calendars
In business, it is common to divide the year for accounting purposes into four quarters, which took three full months included 13 full work weeks. In some sectors in some countries these are in turn divided artificially in 2 months to 4 weeks and a month with 5 weeks. This division can be done in the pattern 5-4-4, 4-5-4 or 4-4-5, the last one the most frequent used scheme. The Economic or - accounting year can basically start at any time of the calendar year, but usually to a month early or a week in early ( Monday or Sunday) in the vicinity, sometimes the definition of the end ( end of the month or on a Sunday or Saturday ) is preferred.
A practical design for a quarter of calendar is the World Calendar by Marco Mastrofini. Each quarter is around three months of the first 31 and the remaining 30 days. In addition, similar to the International perpetual calendar, an additional World Day at the end of the year and in leap years a leap day at the end of June.
In this system, the statistical comparison of previous and subsequent quarters as well as the reasonably possible between prior-year and subsequent years, quarters and months, but not the. Between the preceding and following month
Symmetry 4-5-4
This calendar design uses conform to the ISO 8601 Monday as first day of week. He has in common years four quarters of exactly the same length (13 weeks or 91 days), and each month starts on a Monday. The months - with the traditional names - are either four or five weeks ( ie 28 or 35 days) long; each of the middle month of the quarter is the longer. A switching Week appended of normal length - Additionally December every five to six years - once in 400 years, in the seventh year. The calendar is therefore characterized lunar little.
Bromberg preferred instead of depending on the Gregorian calendar month an astronomically accurate method of calculating leap year in the 52 weeks of switching are distributed uniformly over a 293 - year cycle.
The name Symmetry 454 comes from the fact that each quarter from three months with 4 5 4 weeks there (91 days ). Evenly split quarters are ( quarterly statistics are comparable ) beneficial for the economy ( financial planning) and also for statistical studies. The only exception to this 91 -day quarters is the last quarter in leap years, there is a fifth week of December added. In addition, according to this calendar would have every month a full number of weeks, no partial weeks.
All holidays, birthdays and anniversaries would be fixed and would find every year on the same day in the same week of the year instead. To this end, either retain the previous month-day- date or select the date on the reverse applied new calendar. Would November 9th in Germany for its rich historical importance of a celebration and commemoration, so this one would not find in Symmetry Calendar: In 1918, he was a Saturday, 1938 Wednesday and 1989, a Thursday, in Sym454 but a Tuesday and Sym303130 a Thursday.
Easter could be placed on April 7, whereby all other previously movable Christian holidays would also be fixed. Although the Easter rule only creates the connection between the Gregorian Solar Calendar and the Gregorian lunar calendar, hit the Catholic Church in 1975 before, from 1977 Easter / Pascha always on Sunday after the second Saturday to celebrate in April, whereas in 1997 the World Council of Churches ( WCC) an ajar at the Council of Nicaea calendar freed, purely astronomical scheme proposed.
Symmetry 0-1-0
Alternatively, or in parallel Bromberg suggests a more conservative calendar with 30 - and 31 -day months ( and 37 in leap years December) without straight week number before ( Symmetry 0-1-0 or 30-31-30 ).