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Wikipedia This page uses content from the English Wikipedia. The original article was at Symmetry010 Calendar. The list of authors can be seen in the page history. As with the Calendar Wikia, the text of Wikipedia is available under Creative Commons License. See Wikia:Licensing.


The Symmetry010 Calendar (Sym010) is a proposal for Gregorian calendar reform developed by Dr. Irv Bromberg of the University of Toronto, Canada.

It is a perpetual solar calendar that conserves the traditional 7-day week, and has symmetrical equal quarters of 30+31+30 days each. Unlike its sibling system and successor, the Symmetry454 Calendar, it does not start every month on Monday, but has month lengths closer to the traditional ones. It is retained as an alternative for those who think that the Sym454 design is too "radical" a departure from the Gregorian calendar format.

In a leap year, the Symmetry010 leap week is either appended to December, making it a 37-day month, or it can stand alone at the end of the year as a 13th "mini-month" that was dubbed "Irvember" by Yoel Berznoger of Toronto.

The Symmetry010 calendar is demonstrable in Kalendis by choosing 30+31+30 quarter structure in the Symmetry calendar window. The user can also choose the desired handling of the leap week from the "Symmetry Leap Week" submenu of the "Options" menu. The Sym010 calendar arithmetic is also documented in the public domain, alongside that of the Sym454 calendar.


Symmetry010 year layout by quarter
Quarter 1st month 2nd month 3rd month
Q1
January
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02 03 04 05 06 07
W2 08 09 10 11 12 13 14
W3 15 16 17 18 19 20 21
W4 22 23 24 25 26 27 28
W5 29 30
February
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02 03 04 05
W2 06 07 08 09 10 11 12
W3 13 14 15 16 17 18 19
W4 20 21 22 23 24 25 26
W5 27 28 29 30 31
March
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02
W2 03 04 05 06 07 08 09
W3 10 11 12 13 14 15 16
W4 17 18 19 20 21 22 23
W5 24 25 26 27 28 29 30
Q2
April
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02 03 04 05 06 07
W2 08 09 10 11 12 13 14
W3 15 16 17 18 19 20 21
W4 22 23 24 25 26 27 28
W5 29 30
May
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02 03 04 05
W2 06 07 08 09 10 11 12
W3 13 14 15 16 17 18 19
W4 20 21 22 23 24 25 26
W5 27 28 29 30 31
June
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02
W2 03 04 05 06 07 08 09
W3 10 11 12 13 14 15 16
W4 17 18 19 20 21 22 23
W5 24 25 26 27 28 29 30
Q3
July
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02 03 04 05 06 07
W2 08 09 10 11 12 13 14
W3 15 16 17 18 19 20 21
W4 22 23 24 25 26 27 28
W5 29 30
August
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02 03 04 05
W2 06 07 08 09 10 11 12
W3 13 14 15 16 17 18 19
W4 20 21 22 23 24 25 26
W5 27 28 29 30 31
September
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02
W2 03 04 05 06 07 08 09
W3 10 11 12 13 14 15 16
W4 17 18 19 20 21 22 23
W5 24 25 26 27 28 29 30
Q4
October
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02 03 04 05 06 07
W2 08 09 10 11 12 13 14
W3 15 16 17 18 19 20 21
W4 22 23 24 25 26 27 28
W5 29 30
November
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02 03 04 05
W2 06 07 08 09 10 11 12
W3 13 14 15 16 17 18 19
W4 20 21 22 23 24 25 26
W5 27 28 29 30 31
December
Week
Mon Tue Wed Thu Fri Sat Sun
W1 01 02
W2 03 04 05 06 07 08 09
W3 10 11 12 13 14 15 16
W4 17 18 19 20 21 22 23
W5 24 25 26 27 28 29 30
W7 leap week


(Days 31 through 37 of December are intercalary days that are appended only to the end of leap years.)

Background[]

Balanced quarters are desirable for businesses because they aid in fiscal planning and analysis.

All holidays, birthdays, anniversaries, etc. are permanently fixed. All ordinal day and week numbers within the year are also permanently fixed.

"Friday the 13th" never occurs.

Leap Rule, Arithmetic and Easter[]

See Symmetry454 Calendar

External links[]

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