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Cacatua bird

The Cacatua Calendar year has typically 364 days split in four 91-day quarters or 12 months of 30 or 31 days.

Cacatua months and their length in days
Name Regular Short leap Full leap Long leap
January 30 31 31 31
February 30 30 30 31
March 31 31 31 31
April 30 31 31 31
May 31 31 31 31
June 30 31 31 31
July 30 31 31 31
August 31 31 31 31
September 30 31 31 31
October 30 31 31 31
November 30 30 31 31
December 31 31 31 31
-:- Totals -:-
Quarter 1 91 92 92 93
Quarter 2 91 93 93 93
Quarter 3 91 93 93 93
Quarter 4 91 92 93 93
Year 364 370 371 372

A regular year length is exactly 52 weeks and the next year starts on the same weekday.

Leap years[]

Every fifth year is a leap year. The leap year begins on the same day of the week as the four years before.

In a short leap year, February and November have 30 days and all other months have 31 days. It is called “short” because one day short of one week is added and the next year doesn’t start on the same weekday.

In a full leap year, February has 30 days and all other months have 31 days. The year length is exactly 53 weeks. That occurs every 25 years.

Finally, every 500 years there is a long leap year when every month has 31 days. It has one extra day so the next year doesn’t start on the same weekday.

Leap year cycle (S = short, F = full, L = long)
05 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 ... 500
S S S S F S S S S F S S S S F S S S S F L

The average year length is 365.242 days: (400×364 + 80×370 + 19×371 + 372) / 500 = 182,621 / 500. The full leap cycle with repeating week dates lasts 3500 years. There is also a smaller 175-year repeating week dates cycle which is broken after 500 years by a long leap year.

Year 1 of the calendar starts on 3 January 0001 in the proleptic Gregorian calendar.

Sample Year[]

When the year begins on Monday, for example 2006-2009 or 2046-2049.

Regular Year (364 days)
January / October February / November March / December
Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su
1 2 3 4 5 6 7 1 2 3 4 5 1 2 3
8 9 10 11 12 13 14 6 7 8 9 10 11 12 4 5 6 7 8 9 10
15 16 17 18 19 20 21 13 14 15 16 17 18 19 11 12 13 14 15 16 17
22 23 24 25 26 27 28 20 21 22 23 24 25 26 18 19 20 21 22 23 24
29 30 27 28 29 30 25 26 27 28 29 30 31
April / July May / August June / September
Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su
1 2 3 4 5 6 7 1 2 3 4 5 1 2
8 9 10 11 12 13 14 6 7 8 9 10 11 12 3 4 5 6 7 8 9
15 16 17 18 19 20 21 13 14 15 16 17 18 19 10 11 12 13 14 15 16
22 23 24 25 26 27 28 20 21 22 23 24 25 26 17 18 19 20 21 22 23
29 30 27 28 29 30 31 24 25 26 27 28 29 30
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