Holistic local sustainability; food, water, energy, money, people

The Fixed Calendar

Fixed Calendar © 2021 by Simon D. Cole is licensed under Creative Commons BY-NC-SA 4.0

The Fixed Calendar simplifies dates and accounting because every month has the same number of days. Also, dates and days of the week are fixed – the same calendar can be used every year! To achiever this, there is an extra month called Sol in the middle of the year and two “intercalary days” (Year Day and Leap Day) outside the weekday system.

There are two compelling advantages to the Fixed Calendar. 1/ Business revenue and cost comparisons are simplified. 2/ Ordinary people can memorize it (see below).

I got tired of having to check the Gregorian calendar every fortnight to keep up with the date of rental payments. There had to be a better way, I thought. A little research revealed someone had already solved the problem. I adopted Moses B. Cotsworth’s International Fixed Calendar (see below) and incorporated the Gregorian calendar to create a conversion table (above). The watermark shows the Gregorian months (not dates). I call it the Fixed Calendar. I use it for in-house book-keeping. Keep a copy handy for quick, easy reference.

My conversion table shows how distorted the Gregorian calendar is in comparison to a fixed calendar. There are three more days in the second half of the Gregorian year than the first half! The Fixed Calendar solves this.


The Gregorian calendar quarters are not equal, as shown in the comparison table below.

QuarterGregorian CalendarFixed Calendar
1stJanuary to March= 90 daysJanuary to April 7th= 91 days
2ndApril to June= 91 daysApril 8th to Sol 14= 91 days
3rdJuly to September= 92 daysSol 15 to September 21= 91 days
4thOctober to December= 92 daysSeptember 22 to December 28th= 91 days
Quarters compared: Gregorian vs Fixed

These discrepancies have significant on-going consequences for accounting in business and government financing. Here are some real world examples.

The Fixed Calendar quarters are all equal in length, except for the 4th one if Year Day is included (which I’ve suggested could be an accounting-free holiday where everything is done for free, as envisaged by The Free World Charter). They do not coincide with whole months as in the Gregorian calendar.


The original International Fixed Calendar is a solar calendar proposal for calendar reform designed by Moses B. Cotsworth, who presented it in 1902. George Eastman, founder of Kodak company, promoted Cotsworth’s ‘business friendly calendar’ and his company used it for 60 years. There was significant backing from the business community in the United States and the League of Nations almost adopted it.


Other fixed calendars

Wikipeadia explains the pros and cons of the International Fixed Calendar and calendar reform proposals in general.

The World Calendar – also a fixed calendar – has 12 familiar months and quarters, but the months do not all have the same number of days. Like the Hanke-Henry Permanent Calendar, every first or third month has 31 days and the rest have 30 days.

A major impediment for uptake of the International Fixed Calendar has been complaints from ecclesiastical quarters that it interrupts the seven-day Sabbath cycle. The Hanke-Henry Permanent Calendar solves this by tacking an additional week on to every 5th or 6th year. “So, there would be an extra seven days added to the calendar in, for example, 2026, 2032, and so on. This additional week would serve the same purpose as the extra day we count in a leap year in the present system and keep the calendar in line with the seasons”, Steve Hanke, (2018).

A variation of the Hanke-Henry solution is the 4-4-5 Calendar which divides the standard 52-week year into four 13-week quarters, comprising three periods split into a four-week, four-week, five-week format. “Retailers are the most common users of the 4-4-5 calendar. However, firms in other industries see benefits from this approach to dividing a year into reporting periods. Typical cases include firms tied to the retail trade or for which labor forms a large share of the cost structure. These include consumer goods distributors, manufacturers, and service firms.” NAKISA “Companies who use the weeks-based calendar often do so when there is a natural alignment with core business flows. These flows include customer traffic, shipping, payroll processing, and procurement. These firms often find that period-end cutoff is less complex for those costs, and there is better matching of costs and revenues.” However, this calendar comes with a few challenges, not least of which is the extra length of every 3rd month (see here).


In the meantime the irregularities of the Gregorian calendar will continue to confound us. Apart from sorting the mess out, another significant advantage of a Fixed Calendar is that it can be memorized.

Why a calendar we can memorize?

There are two considerations. One, our resilience as a society in the face of potential disruptions to the digital age from electro-magnetic bombs and solar flares is strengthened. Two, our reliance on paper and Internet-based diaries and calendars (useful for long-term planning) to remind us of what the date is becomes virtually unnecessary; we can do much more in our heads. The affect on our brains of out-sourcing everyday functions is in question. Turning to a smart phone for calendar, spelling and directions assistance leaves me feeling inadequate, because I have a good, long memory of living without any need for them. That might be my hippocampus warning me; use me or lose me. We can lose skills, such as using maps and doing mental arithmetic. Studies show our memories can be impaired (Johansson, A, ABC ‘Our Brain’). Anna Johansson puts it well in her article We need to reduce our dependence on technology if we want to keep innovating:

Instead of introducing a gradual improvement or iterative form of assistance, we’re overwriting entire functions of our brains and bodies. As a metaphor, shoes serve to protect your feet from the dangers of walking on questionable terrain, but if you rely on a wheelchair when you don’t truly need one, your leg muscles would eventually atrophy.



Since the Information Revolution, calendar (and spelling) reform movements have receded into the background. Smart phones among other devices, have taken over the memorizing for us. Few people born after the 1990s have lived without the aid of technology and therefore barely notice the inconvenience of the Gregorian calendar. It seems some technologies are actually serving to stifle innovation of some internationalized habits such as calendars and spelling. Reform movements have evolved in response to changes in power structures and modern technology, which has made innovation more distributed. While once it was governments that debated calendar and spelling reform, now these changes are coming directly from the general public.

Uptake of a new calendar is emerging from below. Businesses are trialing solutions to the real-life, everyday problems the Gregorian Calendar causes such as the 4-4-5 calendar. Quarterly reporting periods are important for businesses and accountants, but wage-earners, renters and many others are affected by fortnightly accounting periods. Quarters that don’t coincide with months are no impediment to the numerate, whose job it is to keep accounts. Fortnights that always start on Sunday the 1st and Sunday the 15th are simple for lay people. The Fixed Calendar is fit for purpose for both business and the general public. The conversion table I’ve created is for grass-roots change-makers. Any business, big or small can adopt it for their in-house accounting purposes. Us ordinary folk can use it to keep track of wages and rent. If it works for you, use it! What matters at this point is that people learn the options available and start putting one of them into practice to see which one works best for them. I’m betting the calendar with the broadest application and appeal will be most likely to succeed.

Fun facts:

  • Although the Fixed Calendar is a solar calendar, not a lunar calendar like the Islamic calendar, it follows the cycles of the moon more closely than the Gregorian calendar, because there are closer to 13 moons in a year than 12 moons.
  • Weeks are unrelated to astronomical phenomenon. They are purely a human construct for dividing months into shorter, more manageable time periods. Sumerians had 10 day weeks, but 7 day weeks became the norm in ancient Israel, and it took off from there.
  • One full orbit of Earth around the Sun takes approximately 365.24 days.
  • The Fixed Calendar has 13 Friday the 13ths, throwing down the gauntlet to the superstitious!
  • Sol means Sun and is northern hemispheric centric.
  • Others have created conversion tables – see the one by freexenon.com.

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