The Forgotten 13-Month Calendar

The Forgotten 13-Month Calendar: A Revolutionary Idea That Almost Replaced Our Year

Category: History | Culture | Timekeeping

---

The Year That Could Have Been: 13 Months Instead of 12

Imagine a year made up of 13 months, each with exactly 28 days, perfectly aligned with the moon and consistent every single year. No confusing leap years, no uneven months with 30 or 31 days, and no struggling to remember how many days are in February. This isn’t science fiction—it’s a real idea that was seriously proposed, studied, and nearly adopted by nations and businesses in the 20th century.

So why don't we use it today?

---

Where Did the 13-Month Calendar Come From?

The most famous version of the 13-month calendar was proposed by Augustus E. Pitman, and later refined by Moses Cotsworth, a British railway engineer, in the early 1900s. It was called the International Fixed Calendar (IFC).

This calendar included:

13 months of 28 days each (exactly 4 weeks per month)

A new month inserted between June and July, named Sol

364 days total, with one or two "blank days" (called “Year Day” and “Leap Day”) that didn’t belong to any week or month

Every date fell on the same weekday every year (e.g., the 1st was always a Sunday)

This calendar was not just a theory. It was used for 26 years by the Eastman Kodak Company (1928–1954), whose founder, George Eastman, was a big supporter of the idea. Employees even had calendar books with the 13-month system.

---

Why Did People Want to Change Time?

The Gregorian calendar (what we use today) is based on solar cycles, but it's highly irregular:

Some months have 30 days, some 31, and February has 28 or 29

Weeks don’t align cleanly with months

It changes every year, making planning and accounting inconsistent

Supporters of the 13-month calendar argued that a more regular system would simplify business, education, payroll, and record-keeping. It would eliminate holidays falling on random weekdays and make life a little more predictable.

---

The Catholic Church and Global Resistance

Despite the elegance of the idea, the calendar faced strong opposition. The Catholic Church was one of its biggest critics. Why?

Because the “blank day” at the end of the year—outside of the weekly cycle—would disrupt the continuous 7-day rhythm that underpins religious practices, including the Sabbath.

Governments were also reluctant to overhaul something as foundational as the calendar. Changing global timekeeping meant rewriting laws, holidays, tax codes, and religious observances worldwide.

---

Other 13-Month Calendars in History

Interestingly, the idea of a 13-month year wasn’t new:

The Mayan Calendar had 13 “months” (called Tzolk’in cycles) of 20 days each.

The Pax Calendar (proposed in 1930) also used a 13-month structure, with similar goals of consistency.

The ancient Lunisolar calendars (used by Jews, Babylonians, and Chinese) sometimes inserted a 13th “leap” month to stay aligned with the moon.

---

Why It Still Fascinates Us Today

Even though the 13-month calendar never became global, it still captivates thinkers, futurists, and those who dream of revolutionizing time. In an age driven by efficiency and automation, the idea of a calendar that never changes feels almost utopian.

Imagine birthdays, holidays, and meetings always landing on the same weekday. You’d never have to check what day of the week your birthday falls on again!

---

Key Characters Behind the 13-Month Calendar

Moses B. Cotsworth – British engineer who developed the International Fixed Calendar

George Eastman – Founder of Kodak, used the calendar for nearly 3 decades

Augustus Pitman – Early promoter of calendar reform

Religious Leaders – Especially in Christianity and Judaism, opposed the disruption of the 7-day week

League of Nations – Debated the idea in the 1920s, but didn’t adopt it

---

Conclusion: Time Is What We Make It

The 13-month calendar reminds us that time, as we live it, is a human invention. Though the Gregorian calendar feels natural, it was imposed by popes, kings, and scholars over centuries. The failed dream of the 13-month year shows just how hard it is to change the very rhythm of society—even when the alternative makes perfect sense on paper.

Still, in an alternate timeline, maybe we’re already living in Sol—the month between June and July—and life ticks forward with quiet, mathematical symmetry.