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The Hawaiian Slice Calendar year is divided into four quarters of equal size.

They are all 13 weeks each.

The week starts on Monday as per ISO 8601. Weeks are numbered from 1 to 52.

Months[]

The months in a quarter are 30, 30 and 31 days long.

On a regular year the calendar follows a TPH pattern (Tomato, Pineapple, Ham):

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

Split week cycle[]

Every five or six years a split week is added at the end of the fourth quarter which ends exceptionally on a Thursday. The first quarter of the following year receives the other half of the week, thus starting on a Friday.

On a year starting with a split week the first three months gain an additional day each. On a year ending with a split week October and December gain one day and November gains two.

The half-week added at the end of the year is numbered 53 and the half-week inserted at the beginning of the next year is numbered zero.

Regular years are 364 days long. The first year of a split week has 368 days and the second year has 367 days.

The pattern of split week years is:

5, 6, 6

After 62 years one six-year cycle is skipped.

After 896 years one six-year cycle is skipped and a new cycle starts.

There are eleven split weeks in a 62-year cycle. There are 159 split weeks in a 896-year cycle. The average year length is:

364 + (159 * 7) / 896 = 365.24219

The current cycle started on Friday 1 January 1909, which began with a split week. The last split week before year 2024 was between 2021 and 2022.

Months when the year begins with a split week[]

January is a Ham month starting on a Friday and has one more day than usual. February is a Tomato month starting Monday with one additional day.

March is a Jalapeño month: it starts on a Thursday. It has one additional day.

The pattern of the first quarter is HTJ:

Ham: January
Mo Tu We Th Fr Sa Su
1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
Tomato: February
Mo Tu We Th Fr Sa Su
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31
Jalapeño: March
Mo Tu We Th Fr Sa Su
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31 32

Months when the year ends with a split week[]

October is the same as usual with one extra day, December is also a Tomato month and has one more day than usual. November is a Jalapeño month with two extra days.

The pattern of the fourth quarter is TJT:

Tomato: October
Mo Tu We Th Fr Sa Su
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31
Jalapeño: November
Mo Tu We Th Fr Sa Su
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31 32
Tomato: December
Mo Tu We Th Fr Sa Su
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31 32

Advantages and disadvantages[]

Pros[]

  1. Most quarters are the same and have a whole number of weeks
  2. All quarters have at least thirteen whole weeks
  3. Only four different month layouts
  4. For the superstitious, Friday the 13th no longer exists
  5. Accurate tracking of the seasons, average year is very close to tropical year
  6. Pizza!

Cons[]

  1. Year length varies by up to four days
  2. Every five or six years, one week is half in that quarter/year, half in the other quarter/year
  3. When that happens some months get extra days
  4. The length of the months differs from the traditional calendar. Some lose their 31, some can go up to 32
  5. Not everyone loves Hawaiian pizza.
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