International Fixed Calendar

The International Fixed Calendar, also known as the Cotsworth plan or the Eastman plan, was a reform proposal intended to replace the Gregorian calendar with a system of equal months and a consistent annual structure. Devised by Moses B. Cotsworth in 1902, it sought to rationalise timekeeping by creating a perennial calendar in which every date corresponded to the same weekday each year. Although never adopted by any nation, it gained notable practical use within the Eastman Kodak Company, where it remained in effect from 1928 until 1989.

Structure and Rules of the Calendar

The International Fixed Calendar divides the year into thirteen months, each comprising twenty-eight days. This structure produces 364 days organised into fifty-two identical weeks. An additional day, known as Year Day, is added at the end of the year after 28 December. This day belongs to no month or week, bringing the total number of days to 365. The calendar retains the Gregorian year numbering, and its New Year’s Day consistently coincides with 1 January in the Gregorian calendar.
The new month, positioned between June and July, was named Sol, reflecting its placement near the Northern Hemisphere’s summer solstice. Cotsworth also suggested Mid as an alternative designation. All months begin on a Sunday and end on a Saturday, creating a uniform weekly structure.
Leap years follow the Gregorian rule: years divisible by four are leap years unless divisible by one hundred, except where divisible by four hundred. In leap years the calendar adds a second special day, Leap Day, inserted as 29 June. This day does not form part of any week, ensuring that the calendrical alignment remains intact. In practice, Year Day and Leap Day produce long weekends, since they are each preceded by a Saturday and followed by a Sunday.
Because the calendar interrupts the conventional seven-day cycle, certain concerns were raised regarding its effects on religious observance, particularly for communities with fixed weekly practices. Nevertheless, the system was almost compatible with other perennial calendar proposals that similarly introduced supplementary days.

Early Precedents and Historical Background

The idea of a thirteen-month calendar has historical roots extending back to the eighteenth century. Lunisolar calendars with fixed associations between dates and weekdays existed in ancient civilisations, and modern reformers sought to revive regularity in timekeeping.
In 1745 Hugh Jones, writing under the name Hirossa Ap-Iccim, proposed the Georgian calendar, a thirteen-month plan named in honour of George II. This arrangement placed the 365th day as a form of Christmas celebration, and its leap-year treatment differed from the Gregorian model. Jones produced a revised version in 1753 that renamed each month after Christian saints.
Further developments emerged in 1849 when Auguste Comte, a leading figure in positivist philosophy, proposed the Positivist Calendar. This scheme also adopted a thirteen-month structure but renamed months after prominent figures such as Moses, Homer, and Shakespeare. It began the year on a Monday and redefined the calendar era, marking year one as 1789, the start of the French Revolution. Its additional days were dedicated to festivals.
Whether Cotsworth was aware of these systems is unclear. His approach echoed earlier models by designating the final day of the year as Christmas and proposing a “Double Sunday,” where both Year Day and the following New Year’s Day would fall on a Sunday. His aim was chiefly practical, focusing on the needs of business and industry. Thus he preserved features of the Gregorian system, including month names and the Sunday-start week layout, common in the United States.

Advocacy and Institutional Support

To promote the calendar reform, the International Fixed Calendar League was founded in 1923. The proposal had been selected by the League of Nations as the strongest among numerous reform submissions. Sandford Fleming, noted for pioneering global standard time, served as the League’s first president. Offices were established in London and later Rochester, New York.
George Eastman, the founder of the Eastman Kodak Company, became a prominent advocate. His company adopted the new calendar for internal use, benefiting from fixed accounting periods and equal month lengths. Despite this business support, opposition emerged from religious groups. Rabbi Joseph Hertz criticised the plan due to concerns about shifting the weekly Sabbath. In political settings, figures such as Sol Bloom voiced objections in hearings and discussions.
During the 1930s the calendar gained international attention. However, the League of Nations ultimately declined to move forward with official adoption in 1937. Without international backing, the International Fixed Calendar League dissolved shortly thereafter.

Legacy and Significance

Although the International Fixed Calendar never achieved global implementation, it remains one of the most thoroughly developed and widely discussed calendar reform proposals of the twentieth century. Its consistent monthly structure offers clear advantages for commerce, accounting and long-term scheduling. Nonetheless, its departure from the uninterrupted seven-day week represented a significant challenge to its acceptance.
Various modern reform efforts draw upon Cotsworth’s ideas, and perennial calendar design continues to interest scholars, historians and advocates of rational timekeeping. The Eastman Kodak Company’s long-term use provides a notable example of how the system functions in practice, demonstrating both its administrative utility and the cultural complexities inherent in altering established temporal conventions.