Symmetry454
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The Symmetry454 Calendar (Sym454) is a proposal for calendar reform proposed by Dr. Irv Bromberg of the University of Toronto. It is a perpetual solar calendar that conserves the traditional 7-day week, has symmetrical equal quarters, and starts every month on Monday.
The proposed calendar is laid out as follows. The last seven days of December are intercalary days and do not occur every year.
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The idea of months having 4 or 5 whole weeks is not new, but was proposed in the 1970s by Chris Carrier for the Bonavian Civil Calendar and by Joseph Shteinberg for his "Calendar Without Split Weeks". Whereas the Bonavian Civil Calendar has quarters of 3 months composed of 5 + 4 + 4 weeks, and Shteinberg's calendar has 4 + 4 + 5 weeks per quarter, the Symmetry454 Calendar has a symmetrical 4 + 5 + 4 weeks per quarter, which is why it is named Symmetry454.
Evenly-balanced quarters are desirable for businesses because they aid in fiscal planning. The only exception to the 91-day quarters are the last quarter of leap years, which has one intercalary week.
All months have a whole number of weeks, so no month ever has a partial week.
Unlike some World Calendar or International Fixed Calendar, there are no individually scheduled intercalary days outside of the traditional seven day week. Alignment of the weekday cycle with New Year Day is accomplished instead by using a Leap Week, which is appended once every 6 or 5 years. In leap years, December becomes a 5-week month. The leap week is shown in bold in the above calendar.
The preferred leap rule is based on a 293-year leap cycle having 52 leap years at intervals that are as uniformly spread as possible:
It is a leap year only if the Remainder of ( 52 × Year + 166 ) / 293 is less than 52.
The 52/293 leap cycle has a calendar mean year of 365+71/293 days, or 365 days 5 hours 48 minutes and 56.5 seconds, which is intentionally slightly shorter than the present era mean northward equinoctial year of 365 days 5 hours 49 minutes.
All holidays, birthdays, anniversaries, etc. are permanently fixed. The ordinal day and week numbers of every Symmetry454 date are also permanently fixed.
The "Kalendis" calendar calculator demonstrates the Symmetry454 calendar and interconverts dates between Symmetry454 and a variety of other calendars.
The Symmetry454 arithmetic is fully documented and placed in the public domain for computer implementation. Officially, Symmetry454 has been running since January 1st, 2006, which was the first New Year Day after it came into existence. Its proleptic epoch, however, was on the same day as the proleptic epoch of the Gregorian Calendar = January 1st, 1 AD.
[edit] Adoption
Irv wants this calendar to be adopted on January 1, 2007 which is a Monday since this calendar and the Gregorian calendar starts on the same date. Irv says the switch won't be costly.
[edit] Easter on a fixed date
Tentatively, Sunday the 7th of April on the Symmetry454 Calendar is proposed as a fixed date for Easter, based on a frequency analysis of the distribution of the Gregorian or Astronomical Easter dates. There are only a few dates that Easter can possibly land on within the Symmetry454 Calendar, because only day numbers divisible by 7 can be a Sunday. The 3 highest-frequency dates upon which Easter can land are March 28th, April 7th, and April 14th. Selecting the middle date, April 7th, would fix Easter at its median position within its distribution range.
