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The Jubilees Leap Week Calendar, created by Walter Ziobro, is an adaptation of the 364-day calendar that is described in several ancient Hebrew texts, see Qumran Calendar and Enoch Calendar.  The year begins on a Sunday close to the Southward Equinox, and the 30 day months are named for letters in the Hebrew alphabet:

Months
Name Length
Sunday of the West  1 day    
א Alef   30 days
ב Bet     30 days
ג Gimel   30 days
Sunday of the South  1 day
ד Dalet   30 days
ה He      30 days
ו Vav     30 days
Sunday of the East  1 day
ז Zayin   30 days
ח Chet   30 days
ט Tet     30 days
Sunday of the North  1 day
י Yad     30 days
כ Kaf  30 days
ל Lamed 30 days
37 days in leap years

The epoch of the calendar is Sunday, September 17, 4000 BCE of the Proleptic Gregorian Calendar (October 19, 4001 BC of the Proleptic Julian Calendar), or Julian Day 260349.5.  The Era is called the Lucian Era (Anno Lucis), so Sunday, September 17 of 2000 CE/AD (Gregorian) would be Sunday of the West, 6001 Anno Lucis.

Leap rules[]

The leap week is added to the final month of the longest season of the year, and so shifts from one season to the following season currently every 5,100 years.  So, since Anno Lucis 1 (4000 BCE), the leap week would have been added to the following months during the indicated years:

Tet:   1 - 5,100 A.L.   (4,000 BCE - 1,100 CE/AD)
Lamed:    5,101 - 10,200 A.L.   (1,101  - 6.200 CE/AD)
Gimel:  10,201 - 15,300 A.L.   (6,201 - 11,300 CE/AD)
Vav:    15,301 - 20,400 A.L.   (11,301 - 16,400 CE/AD)

The leap week is added 9 times every 50 years (a jubilee cycle), except that it is added only 8 times in every 8th jubilee, such that there are a total of 71 leap weeks every 400 years, a period of 146,097 days, which is exactly the same number of days in 400 Gregorian years. The leap week is added to the years in a 50 year cycle in a general pattern of 6-5-6-5-6-6-5-6-5(6) years, which shifts by one year every 6 out of 8 jubilees according to the following schedule:

Schedule for years with leap week in 50-year Jubilee cycle
Jubilee   First leap year Intervals to subsequent leap years
1 +6 +5 +6 +5 +6 +6 +5 +6
2 +6 +5 +6 +5 +6 +6 +5 +6
2 +6 +5 +6 +5 +6 +6 +5 +6
3 +6 +5 +6 +5 +6 +6 +5 +6
4 +6 +5 +6 +5 +6 +6 +5 +6
5 +6 +5 +6 +5 +6 +6 +5 +6
5 +6 +5 +6 +5 +6 +6 +5 +6
6 +6 +5 +6 +5 +6 +6 +5
Years of the 400-year cycle that have leap weeks, J = {6, 6, 5, 6, 6, 6, 5, 6}
Jubilee +J +6 +5 +6 +5 +6 +6 +5 +6
1 001 007 012 018 023 029 035 040 046
2 052 058 063 069 074 080 086 091 097
3 102 108 113 119 124 130 136 141 147
4 153 159 164 170 175 181 187 192 198
5 204 210 215 221 226 232 238 243 249
6 255 261 266 272 277 283 289 294 300
7 305 311 316 322 327 333 339 344 350
8 356 362 367 373 378 384 390 395
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