International Fixed Calendar

The International Fixed calendar (also known as the International Perpetual calendar, the Cotsworth plan, the Eastman plan, the 13 Month calendar or the Equal Month calendar) is a solar calendar proposal for calendar reform designed by Moses B. Cotsworth who presented it in 1923 providing for a year of 13 months of 28 days each, with one day at the end of each year belonging to no month or week. Though it was never officially adopted in any country, it was the official calendar of the Eastman Kodak Company from 1928 to 1989.

Rules

The calendar year has 13 months each with 28 days (divided in exactly 4 weeks) plus an extra day at the end of the year not belonging to any month (and so 365 days). Each year coincides with the corresponding Gregorian year.

The months have the same names as those of the Gregorian calendar, except that a month called Sol is inserted between June and July.

There is one leap year, with 366 days, every four years in order to compensate, as in the Gregorian calendar, the ~365.25 days per year. On that year, a leap day is inserted after June and before Sol.

Days that do not belong to a month are deemed to be outside the week and always occur between a day deemed Saturday and a day deemed to be Sunday.

The first day of each year, January 1, is deemed a Sunday and every subsequent day that belongs to a month is deemed to be in the conventional 7-day week.

Because each month consists of exactly four weeks, the first day of each month and every seventh day after that for the rest of the month is deemed to be a Sunday, the second day of each month and every seventh day after that for the rest of the month is deemed to be a Monday, and so on. Therefore, each month begins on a Sunday and ends on a Saturday, just like each conventional week.

This causes all months to look like this:

Sun	Mon	Tue	Wed	Thu	Fri	Sat
1	2	3	4	5	6	7
8	9	10	11	12	13	14
15	16	17	18	19	20	21
22	23	24	25	26	27	28

The 13 months and extra days occur on the following Gregorian dates:

Month	Starts	Ends
January	January 1	January 28
February	January 29	February 25
March	February 26	March 25*
April	March 26*	April 22*
May	April 23*	May 20*
June	May 21*	June 17*
Leap Day	June 17
Sol	June 18	July 15
July	July 16	August 12
August	August 13	September 9
September	September 10	October 7
October	October 8	November 4
November	November 5	December 2
December	December 3	December 30
Year Day	December 31

*These dates are a day earlier in a leap year.

History

The International Fixed Calendar League was founded in 1923 by Moses B. Cotsworth, with offices in London and later in Rochester, New York. It ceased activities in the 1930s.

George Eastman of the Eastman Kodak Company was a fervent supporter of the IFC, and instituted its use at Kodak in 1928, where it remained in use until 1989.

In recent years, there have been attempts to revive the plan.^{[citation needed]}

The International Perpetual calendar is based on the Positivist Calendar published in 1849 by French philosopher Auguste Comte (1798–1857). Comte based his calendar on Polynesian calendars. The main difference between the International Perpetual calendar and the Positivist calendar is the names Comte gave to months and days. The months in the Positivist calendar were, in order: Moses, Homer, Aristotle, Archimedes, Caesar, St. Paul, Charlemagne, Dante, Gutenberg, Shakespeare, Descartes, Frederic and Bichat. Every day of the year was likewise named. Positivist weeks, and Positivist months, begin with Monday instead of Sunday. Whereas the Positivist and Sol calendars place the leap day at the end of the leap year, the International Fixed Calendar and the World Calendar both place it after June.

Advantages

Several advantages do exist on this calendar, mainly related to its organization. When compared to the Gregorian, it is clear that this calendar is much simpler and practical:

• every year has exactly 52 weeks divided in 13 months;
• each month has exactly 28 days divided in 4 weeks
• every month/year's day has the same week day (nth month/year day is always the m'th week's day, where m is the remainder of n/7).

Compared to other proposals, this calendar keeps the same days per year, and the same days per week, which are two advantages that ease possible change.

In Gregorian calendar, the New Year's Day is a world holiday. On this proposal, that day is a Sunday by definition, which obsoletes the world holiday, substituting it by a weekend day.

On this proposal, the number of national holidays that do not fall on weekends are no longer year-dependent. This no longer causes certain years to have more workdays than others.

Disadvantages

For the superstitious, a disadvantage to this format is that every month includes a Friday the 13th, and this date occurs thirteen times every year.

Thirteen, being prime, is not evenly divisible, putting all activities currently done on a quarterly basis out of alignment with the months.

Several religious groups oppose any interruption of the seven-weekday sequence.

See also

• Leap week calendar
• World Calendar

External links

• Article on the International Fixed Calendar League at the International Institute of Social History Archives.
• Article about the Cotsworth Calendar of George Eastman.