In the early 20th century, the world came surprisingly close to adopting a radically different calendar system. The International Fixed Calendar, with 13 months of exactly 28 days each, gained serious momentum and was nearly implemented by several major corporations and even entire countries.
• 13 months of exactly 28 days each (364 days)
• 1 extra day called "Year Day" (not part of any month)
• 1 leap day every 4 years called "Leap Day"
• Every month identical: 4 weeks of 7 days
• Same date = same weekday every month
The system was elegantly simple. Every month would have exactly four weeks. The 15th would always fall on a Sunday. Christmas would always be on the same day of the week. Business planning would become incredibly straightforward because every month and quarter would be identical in structure.
The 13th month was to be called "Sol" and placed between June and July. The year would look like this: January, February, March, April, May, June, Sol, July, August, September, October, November, December.
The proposal gained serious traction in the 1920s and 1930s. The League of Nations studied it extensively, and it had powerful supporters:
Corporate backing: Kodak implemented the 13-month calendar internally from 1928 to 1989, using it for payroll and business planning. Other companies like Xerox and R.G. LeTourneau Inc. also adopted it.
Government interest: The Soviet Union seriously considered adopting it as part of their broader calendar reforms. Several smaller nations expressed willingness to be early adopters.
Academic support: Economists and business leaders praised its logical structure and potential for simplifying international commerce.
• 1849: Auguste Comte's Positivist Calendar (13 months)
• 1902: Moses Cotsworth's International Fixed Calendar
• 1930s: League of Nations serious consideration
• 1937: World Calendar Association formed
• 1950s: United Nations studies calendar reform
The advantages were compelling:
Business benefits: Every quarter would have exactly 91 days (13 weeks). Monthly comparisons would be meaningful since every month had the same structure. Payroll calculations would be simplified.
Personal convenience: Birthdays and holidays would always fall on the same day of the week. Planning would be easier since the 1st was always a Sunday, the 15th always a Sunday, etc.
International standardization: A single, logical calendar system could eliminate confusion between different national calendar traditions.
But the reform faced significant obstacles:
Religious opposition: Many Christian denominations objected because the "blank days" (Year Day and Leap Day) would disrupt the continuous seven-day weekly cycle that had been maintained since biblical times.
Jewish concerns: The disruption of the weekly cycle would make it impossible to observe the Sabbath consistently, as the blank days would cause the days of the week to shift.
Cultural resistance: People were attached to traditional month names and lengths. The idea of a 13th month seemed superstitious to many.
Practical complications: Existing contracts, legal documents, and systems would all need to be converted. The transition costs would be enormous.
The closest the world came to adoption was in the 1930s when the League of Nations formed a committee to study calendar reform. The committee recommended the International Fixed Calendar, but World War II derailed the initiative.
After the war, the United Nations revisited calendar reform in the 1950s, but by then the momentum had faded. The practical difficulties of coordinating a global change seemed insurmountable, especially with the world divided by the Cold War.
Other calendar reform proposals included:
The World Calendar: 12 months with quarters of 31-30-30 days, eliminating the need for a 13th month but still requiring blank days.
Perpetual Calendar: Various proposals to make the calendar repeat exactly every year, eliminating the need to print new calendars.
Decimal Calendar: Attempts to create 10-month years to align with the metric system, though these gained little support.
Interestingly, some organizations continued using reformed calendars internally:
• Kodak used the 13-month calendar for 61 years (1928-1989)
• Some accounting firms still use 13-period years for financial reporting
• The entertainment industry often uses 13-week quarters for television seasons
The failure of calendar reform illustrates the power of tradition and the difficulty of changing fundamental social systems. Even when a proposed change is logically superior and has significant support, the practical and cultural barriers can be insurmountable.
Today, with our globally interconnected world, calendar reform would be even more difficult. Computer systems, international agreements, and cultural practices are all deeply embedded with our current calendar system.
The 13-month calendar remains one of history's great "what if" scenarios—a logical, elegant system that could have simplified timekeeping worldwide, but fell victim to the immense inertia of human tradition and the practical challenges of coordinating global change.