The weirdness of the present calendar

When it comes to the calendar, there are only two things that are fixed by nature that we have no control over: the length of the day and the length of the year as approximately 365¼ days. All the other divisions are purely arbitrary. While some cultures have calendars that ascribe significance to the lunar months that last approximately 28 days, it is safe to say that we can safely ignore it. How many of us keep track of the lunar phases from day to day anyway? But despite the fact that we can subdivide the days in the year in any way we like, we have arrived at a system that makes little sense. We divide the year into four months of 30 days each, seven months of 31 days each and one month of 28 days, becoming 29 in a leap year.

But the really weird thing is the length of the week as seven days. As a result of the present system, any given date will fall on a different day of the week from year to year, which makes long term planning of events more difficult.

Part of the problem is that the number 365 only factors into 5 and 73. So to have a regular pattern, we would need to have five divisions of 73 days each or 73 divisions of five days each. 73 weeks of five days each would be workable, though this might mean a three day work week if we want to keep a two day weekend, or we would have just a single day off after four days.

The number 364 has many more factors (2, 4, 7, 13, 14, 26, 28, 52, 91, 182). It is the pairs of factors 13×28 and 4×91 that were used as the bases of proposed new calendars that would be more regular.

In should not be surprising that there have been repeated calls to change the system. In a review of a book The Week: A History of the Unnatural Rhythms That Made Us Who We Are by historian David M. Henkin, Jill Lepore examines the history of the seven-day week and the efforts to change it. What surprised me as that these efforts persisted until the mid-twentieth century before they were abandoned.

Lepore says that historically there have been five-day, eight-day and ten-day weeks and the seven day week established its hegemony largely due to the domination of Christianity and Islam.

No one has ever really been able to topple the seven-day week. French revolutionaries tried to institute a ten-day week. Bolsheviks aimed for a five-day week. No one tried harder than Miss Elisabeth Achelis, a New York socialite, heir to the American Hard Rubber Company fortune, and an admirer of Melvil Dewey, he of the Dewey decimal system and simplified spelling.

Even as the seven-day week was “going global,” as Henkin puts it, toward the end of the nineteenth century lots of people began pointing out how awkward it was that the sixteenth of April fell on a Saturday in 1881 but on a Sunday in 1882. Especially after the adoption of an international standard of time, in 1884 (and the promulgation of time zones), many commentators expected a global standardization of the calendar, to remedy the quirkiness of the moon. In the eighteen-nineties, Moses B. Cotsworth, an Englishman who worked as a statistician for a British railway company, began pondering the possibility of a more efficient calendar, one that would make it easier to compare revenues from month to month and week to week. He devised the International Fixed Calendar, which consisted of thirteen months of twenty-eight days each, with one extra day following the last day of December and one more, at the end of June, in leap years. The new month, between June and July, would be called Sol. (Auguste Comte had come up with nearly the same solution in 1849; under his plan, the extra day every year would be devoted to “all the dead” and the three-hundred-and-sixty-sixth day in leap years to “holy women.”)

Achelis endorsed a [World Calendar] of twelve months made up of four equal quarters of thirteen weeks, or ninety-one days. “Each year begins on Sunday, January 1,” she explained; every quarter begins on a Sunday, and ends on a Saturday. “Every year is comparable to every other year; and what is of utmost importance, days and dates always agree.” If you were born on a Friday, your birthday would always fall on a Friday. In deliberations at the League of Nations, the World Calendar beat out many rivals, including a proposal for a year of four thirty-five-day months plus eight twenty-eight-day months, and proposals for a five-, six-, and ten-day week.

The World Calendar created new days: Year-End Day, Leap-Year Day, extra Saturdays in December and June. Once every year and twice every four years, in other words, the World Calendar had an eight-day week.

Apparently some people in the US were upset that adopting a new calendar meant that the ‘Fourth of July’ would have to be called something else, as if Independence Day was not enough. That was not all. The new calendars also conflicted with religious routines.

If adopted, it would have thrown out of whack the seventh-day Sabbath of Judaism, Christianity, and Islam, as the League for Safeguarding the Fixity of the Sabbath Against Possible Encroachment by Calendar Reform explained. “Six days do they labor and do all that they have to do but the seventh they worship and rest,” Time reported in 1934. “If one extra day alone were introduced into their year they would eventually be observing the Sabbath on weekdays while the rest of the world worked.”

In 1955, when the United Nations proposed yet another study group to take up the subject of the World Calendar, the U.S. State Department opposed it. So did Congress.

And that ended that.


  1. moarscienceplz says

    It took several decades for the Protestant world to accept the change from the Julian calendar to the Gregorian, mostly because it was invented by Catholic scholars, even though it was way more logical and greatly reduced the number of adjustment days that had to be dealt with.
    I’d rather we USAians could focus on fully accepting the Metric System. Nearly everyone agrees that STEM education is important for our kids, but the practical effect of their parents’ and grandparents’ refusal to accept a tiny bit of change in their own lives is that we have to waste precious school hours teaching two sets of measurement systems to our kids for the forseeable future. We buy our sodas by the liter, but we still buy our milk by the gallon and quart. We buy our gasoline by the gallon, but we need millimeter socket wrenches to repair our cars. If I plan to travel out of the country, and a weather forecast predicts it will be 31°, will I need to pack shorts and a shady hat, or a parka? It’s just nuts what we put ourselves through.

  2. billseymour says

    I remember reading an essay by Isaac Asimov many years ago in which he proposed what he called a “world seasonal calendar” which was basically the same thing as what’s called the “World Calendar” above, except that he called the four divisions “seasons” instead of “quarters.”  Did Asimov claim to invent something he didn’t?  (I don’t remember him specifically claiming that he invented it, so maybe not; although this link attributes the proposal to him.  Could the difference be that Asimov would begin the year specifically with the winter solstice?)

    I agree that this would be a good step forward.  I’d even be willing to put up with the fundigelicals screaming bloody murder at a tiny reduction in their ability to screw up the lives of everybody else.  (It probably wouldn’t quiet them at all to point out that they’d get an extra day of worship every year.)

  3. says

    Simple proposals could include:

    1) Thirteen months, twelve of 28 days and the last either 29 or 30 in a leap year. Every month of a year will start on the same day.

    2) A 360 day year, with a five or six day holiday. You could have six day weeks, four work/school days and a weekend.

    The QWERTY keyboard and current calendar have massive intertia from common use and mass manufacturing. The keyboard might die because we can replace typing with voice activation. But replacing the calendar would require rewriting the entirety of software and record keeping, something almost everyone would opose.

  4. anat says

    .. and if every 28 day month starts on a Sunday, then every month will have a Friday the 13th! (But of course, if these months start on any day other than Sunday Friday the 13th will never exist.)

  5. John Morales says

    But the really weird thing is the length of the week as seven days. As a result of the present system, any given day will fall on a different day of the week from year to year, which makes long term planning of events more difficult.

    Say the event is held on the Tuesday of the second week of each month, why is that problematic for long-term planning?

  6. birgerjohansson says

    A Swedish cartoonist suggested introducing a new month between November and December. The month would be called “Mörv!” , an onomatopoetic expression people make when they are exposed to the damp cold of the period.

  7. birgerjohansson says

    The introduction of new months in the Roman calendar we inherited was pretty arbitrary. But at least they had the sense of consulting a greek astronomer, leading to the leap year.
    The muslim calendar is still a lunar calendar. The priesthood in Saudi Arabia still cling to the privilege of announcing when a new month will begin, based on observations (that can be reliably predicted long in advance, but never mind).

  8. Rob Grigjanis says

    Changing the calendar would be more trouble than it’s worth. Apart from having to change a shitload of software, there’s the small matter of getting everyone to agree, and somehow synchronise. And I don’t think the current system is bad enough to warrant a change.

    It’s a bit like the idea of replacing π with τ=2π. Not gonna happen.

  9. Owlmirror says


    As a result of the present system, any given day will fall on a different day of the week from year to year

    I think you meant “any given date“.

    [I have corrected it. Thanks! -MS]


    It took several decades for the Protestant world to accept the change from the Julian calendar to the Gregorian

    Or rather, several centuries.

  10. Silentbob says

    I think it would suck if every year your birthday were on a Monday, versus getting a Saturday every year (or whatever the workdays/weekend days would be).
    I’m always happy when the cycle comes around and my birthday’s on a weekend, or at least a Friday. 🙂
    And yes I know celebrating birthdays is itself arbitrary — just sayin’.

  11. Silentbob says

    The way things are, the people I feel most sorry for are those born on Feb 29th.

    Imagine having to wait until your eighties so celebrate your 21st birthday. 😉

  12. John Morales says


    Imagine having to wait until your eighties so celebrate your 21st birthday.

    Well, aside from the incongruity of being on your eighties to celebrate your 21st birthday, it would be most excellent. If only!

    Birthdays, I’ve found, are yet another day of social obligation. Most annoying.

  13. says

    This is entirely from memory, so I could easily be mistaken, but IIRC the World Calendar consists of twelve months (January through December) arranged in four quarters of 91 days each in which the first month of each quarter (January, April, July, October) has 31 days and all the others 30. Year End Day (after 30 December) and Leap Year Day (after 30 June) fall between Saturday and Sunday and so don’t change the weekdays for the next quarter. (The text above says they are extra Saturdays, which could well be correct, but I remember them as days without a weekday designation.)

    Asimov’s proposal had no months but only four seasons, designated A, B, C and D. A (winter in the Northern Hemisphere, summer in the southern) would progress from A-1 to A-91 and then be followed by B-1. I don’t remember how the extra day (or in leap years days) fitted in; I assume it would have been between D and A at the end of the year.

    Somewhere I read of a proposal like the World Calendar but without the Year End and Leap Year days--instead most years would have 364 days (like the old sectarian Jewish calendar in Jubilees), but every five or six years an extra week would be interpolated into the mix, making a 371 day year to bring the seasons back into alignment. Of course the Muslims have done quite well with a 354 or 355 day year that does not align with the seasons; I don’t know how essential that seasonal-alignment thing is anyway.

  14. beholder says

    @1 moarscienceplz

    I’d rather we USAians could focus on fully accepting the Metric System.

    But all the scientists are using the SI system now. We can just switch to that instead. 😉

    For that matter, we should do away with calendars and switch to a fixed epoch, e.g. International Atomic Time. No ambiguity, just add one every 86,400 SI seconds. The math is far simpler.

  15. Holms says

    The tropics in particular do not have four discrete seasons, having only wet and dry. Any calendar relying on seasons is necessarily going to be very local.

  16. says

    John Morales: “the planet is not uniform in its seasons, nor necessarily Eurocentric”

    I assume that’s why Asimov gave his seasons letter designations rather than names like “Winter,” “Spring,” “Summer,” and “Autumn.” “A” is the season that begins with the solstice in which the north pole of the earth’s axis is pointing away from the sun (loosely speaking) known as the winter solstice in the northern hemisphere and the summer solstice in the southern; it ends with the equinox (spring in the northern hemisphere and autumn in the southern). B would then be the astronomical season called Spring in the northern hemisphere (Autumn in the southern), and so on. Asimov probably explained that in his essay, but I lost my collection of F&SFs along with the bulk of my library a decade or so ago and can’t check the point.

    The planet may not be Eurocentric, but the system of timekeeping in use is--check the position of the International Date Line for one example. The calendar in use in large parts of the world certainly is, with its months named after European deities (Janus) or political figures (Augustus Caesar). There are many parts of the world in which other (“not necessarily Eurocentric”) calendars are in use; one astronomical calendar simply numbers the days from an arbitrary point in the past.

    In a novel I once read (as far as I know still unpublished) set in the asteroid belt centuries from now the characters measured time in intervals of a million seconds, known as “megasecs” (or something like that). There is no special reason that the calendar has to be tied to the motions of the earth except that this is where we happen to live, and it is convenient for the calendar to give us some idea of when the salmon are going to start their run, or when the corn needs to be planted. It is not necessary; as I noted in my previous comment the Muslims have done quite well with a calendar that corresponds to the phases of the moon but ignores the changes of the seasons. Calendar reform in the West, however, has been obsessed with keeping the days of the year in sync with the motions of the planet.

  17. says

    Holms: “Any calendar relying on seasons is necessarily going to be very local.”

    The astronomical seasons run from solstice to equinox and equinox to solstice and are the same throughout the planet. (Well, the nomenclature differs between the northern and southern hemispheres.)

  18. cartomancer says

    Bring back Mercedonius! Everyone used to like Mercedonius before that rotter Caesar did away with it. It was named after getting paid, for goodness’ sake! Nice and easy to remember too -- January, first 23 days of February, Mercedonius (though only when the Pontifex Maximus said so), rest of February, March, April, etc.

  19. mnb0 says

    @2 Sbh: the astronomical may be the same throughout the planet, they still mean zilch in the tropics. I know, because I’ve been living there for a few decades.

  20. Owlmirror says

    In a novel I once read (as far as I know still unpublished) set in the asteroid belt centuries from now the characters measured time in intervals of a million seconds, known as “megasecs” (or something like that).

    You probably are not thinking of “A Deepness in the Sky”, by Vernor Vinge (since that was published in 1999), but that novel does also have a deep-space-faring culture in the far future that uses metric seconds for timekeeping.

    There’s even a bit in there about how the timekeeping system is supposedly based on the first man stepping on the moon, but there’s some sort of adjustment because it’s actually some amount (whatever the number of seconds between July 20, 1969 and Jan 1, 1970) off, because Jan 1, 1970 is the actual zero-point of the Unix Epoch that underlies all of their computer systems.

  21. Steve Morrison says

    Asimov probably explained that in his essay

    He did say exactly that. I looked it up, and the essay is “The Week Excuse,” from the June 1972 F&SF, reprinted in The Tragedy of the Moon.

  22. John Morales says

    sbh @19, from my link: “The Nyoongar calendar includes six seasons.”

    (A, B, C, D, E, F)

  23. Rob Grigjanis says

    WMDKitty @27: Nowadays, in the Northern Hemisphere, most of us consider the summer solstice to be the start of summer. That it is also called midsummer day is a relic of the Anglo-Saxon reckoning, which had only two seasons; summer and winter. Midsummer fell about halfway between planting and harvesting.

  24. billseymour says

    It has always seemed to me that the weather seasons ought to lag the astronomical ones by 90 degrees.  The solstices ought to be when the temperatures are changing most rapidly; the equinoxes should be when the temperatures start moving in a more moderate direction.

    I know that actual weather is way more complicated than that.

  25. anat says

    As someone who grew up in a sub-tropical climate I have a very different image of the seasons: The time I most associate with ‘rebirth of nature’ is not spring but early autumn, when the rain is (or should be) back, the time most associated with death is the late summer. And harvest starts in spring and ends in early autumn, as it had been for a long time. (Except nowadays with increased variety of crops something is being harvested any time of year.)

  26. says

    WMDKitty @27: I’ve always felt that the solstices and equinoxes should mark the midpoints of the seasons, but nobody consulted me in drawing up the rules. The astronomical seasons--which IIRC are what Asimov was working with--run from solstice to equinox (summer and winter) or equinox to solstice (autumn and spring). Neo-pagans, or some of them anyway, begin the seasons at the midpoint between solstice and equinox, making Imbolc (2 February), Beltane (1 May), Lammas (2 August), and Samhain (1 November) the start of the seasons--or something like that. I personally observe an eight-season model based on the length of days in which we (in the northern hemisphere outside the tropics) have just begun Yuletide which will be followed by Sheol in mid-January. Here in Portland (Oregon) there are really only two seasons, as the old saw used to put it--the rainy season, and the rainier season. Or maybe it was the wet season and the wetter season. My memory is not what it once was.

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