Dear Calendar People
I have seen many notes about calendar reform here. But one thing I thought about making explicit is that it is impossible to produce a solar calendar that achieves all three of the following objectives:
(a) All years (and months) have a whole number of weeks. Each year (and month) starts on the same day of the week.
(b) The seven day week is used without any kind of interruption.
(c) A simple leap year rule is used based on the fact that the year is approximately 365.25 days long.
It is possible to produce a solar calendar that achieves any given two of these objectives. The Gregorian calendar does (b) and (c).
Cotsworth Fixed Calendar Raventos Symmetrical Perpetual Calendar Bill Hollon's Fixed Week Calendar The Raenbo Calendar New Millennium Calendar World Calendar William Cupp's Second 'Metric' Calendar Proposal My Rainbow Alphabet Calendar
(a) & (c) Calendars
Many proposed calendar reforms do (a) and (c)
Cotsworth Fixed Calendar(13 months, extraday at end, leapday at end of 6th month)
Raventos Symmetrical Perpetual Calendar(13 months, extraday and leapday at end)
Bill Hollon's Fixed Week Calendar(12 months 6 day week, extradays almost evenly distributed)
The Raenbo Calendar(12 months 6 day week, extradays at quarters) Uses base-12 counting.
New Millennium Calendar(12 months 6 day week, extradays in April) Why April?
World Calendar(12 part-week Months of 30 or 31 days, extraday at end, leapday at end of 6th Month)
William Cupp's Second 'Metric' Calendar Proposal(12 part-week Months 8 day week extradays at quarters)
My Rainbow Alphabet Calendar(52 weeks A-Z,a-z, extraday in Z, leapday in z)
Colligan's Pax Calendar Bonavian Civil Calendar Pragmatic Civil Calendar
(a) & (b) Calendars
For the uninterrupted 7 day week calendars that do (a) and (b) have been
Colligan's Pax Calendar(13 months of 4 weeks + leap week )
Bonavian Civil Calendar(12 Months of 4 or 5 weeks)
Pragmatic Civil Calendar(12 part-week months 30 or 31 days, leap week spread over 7 months)
Walter Ziobro's calendar (12 part-week months 30, 31 or 37 days)
At beginning of CALNDR-L March 1997 Archive
ISO Week Calendar
ISO Week Calendar(52 or 53 weeks) and its variant My playing card calendar
(b) & (c) Calendars
Then one could have the simple leap-year rule and an uninterrupted 7day
week, if you gave up the whole week years (i.e., the calendar is not
perpetual). The rules for finding the day of the week could be made simpler
by making the calendar more regular. E.g.
(1) Jan, Apr, July, Oct, Dec + Jun in leap years 31 days others 30 day (similar to world calendar)
(2) Feb, Apr, Jun, Aug, Oct + Dec in leap years 31 days others 30 day (amenable to simplified doomsday method)
(3) Jan, Mar, May, Aug, Oct + Dec in leap years 31 days others 30 day (similar to Bill Hollon's Fixed week calendar)
(4) All months 30 days extra month every 4 years of 21 days shortened to 18 days every 400 years (produces regular 7 year cycle interrupted to restart every 400 years)
I have not found any on the Internet that is not a renamed form of the Gregorian Calendar with possibly different leap year rule.
Another one I forgot to mention is simply to have the New Year on March 1st. This eliminates most of the complications arising from leap years, by having the leap day at the end of the year.
Tuesday Queen of Hearts
Blueday little l [l5]
Abridged version of the following conversation on CALNDR-L:
Date: Tue, 15 Sep 1998
From: RICK MCCARTY
Subject: Re: Calendar Reform - Only 2 out of 3
May I plead for The Long-Sabbath Perennial Calendar as employing a device that would satisfy 3 out of 3 of Karl's list of calendar disiderata.
I think you can get all three of what Karl labled (a) (b) and (c) if you give up the fiction that a calendar day lasts 24 hours. And most of the world has seen fit to give up that fiction.
Almost everyone observes a 23-hour calendar day and a 25-hour calendar day once a year.
The Long-Sabbath Plan is on the Home Page for Calendar Reform; http://ecuvax.cis.ecu.edu/~pymccart/calendar-reform.html
1998-09-16, Wednesday :
Yes, but a 36-hour "day" is stretching it a bit too far, IMHO. No matter what you call it, I can't accept a definition of a "day" which names as 2 days" a period of 72 hours -- which normally includes 3 sunrises, 3 sunsets, etc.
refers to the 7 day week using the day night cycle as practised for a long time. He also made the point that unlike daylight saving time, the Long-Sabath plan does not maintain an avarage date length of 24 hours and that it is not possible to determine a long-sabath day of week from a Julian Day number without referring to the rules of the calendar.
I feel this will remain as common standard for the "day" as long as international travel is not faster (e.g. point-to-point between all metropoles in less than three hours) and more common (i.e. enabling "international commuting"). If this technology existed, it would make sense for each family to live by a special calender. But for now, day and night is best.
Date: Wed, 16 Sep 1998 12:34:39 -0500
From: Jim Eikner
1) It is solely based on 365 1/4. ... I see this as no different than a 365 day calendar with a .25 annual shortfall. Neither is accurate. Both require adjustment at some future date ...
2) Your original requirements were for 12 months, not 12 months of equal length. That too could be designed but the shortfalls and corrections would be a nightmare ...
The above emails have been subject to editing - refer to the CALNDR-L archive for full text
Karl Palmen's Calendars
Essays on mathematical themes
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