The Skyrope Calendar is based on a thirteen-month year where most months have 27 days, like the Togys Esebi Calendar of the Kazakh nomads. However Skyrope Calendar is rules-based not observation-based.
The Skyrope year begins on a new moon day around April-May. The intention is that the moon aligns with the Pleiades cluster (Seven Sisters) when its crescent appears.
The first four months of the year have 28 days. The following nine months have 27 days each. They are named after features of the Steppe:
- Altai
- Bukhara
- Volga
- Gobi
- Danube
- Carpathians
- Nomad
- Manul
- Pamir
- Samarkand
- Taiga
- Tian Shan
- Ural
- Wolf (leap)
Intercalation[]
Since a regular year is shorter than the tropical year (355 days), an additional month is added on leap years to realign with the seasons.
The Skyrope calendar follows a 30-year leap cycle with a 11-year subcycle. Leap years are distributed as follows:
| 3 | 6 | 8 | 11 |
| 14 | 17 | 19 | 22 |
| 25 | 28 | 30 |
The additional month is added at the end of the year and has 28 days, unless the year number ends with 1 or 2 then it has 27 days (short leap year).
Every 600 years a supercycle is inserted. It has a 5-year subcycle instead of 11-year which means there are twelve leap years instead of eleven:
| 3 | 5 | 8 | 10 |
| 13 | 15 | 18 | 20 |
| 23 | 25 | 28 | 30 |
The supercycle leap months have 28 days except for years 13, 18, 23 and 28 of the supercycle that have 27 days.
That makes a leap cycle of 630 years with an average year length of 365.24127 days and an average month length of 27.32154 days.
Lunar Calendar[]
Since the Skyrope Calendar year begins on a new moon, it is closely related to the lunar cycle.
A lunar calendar is derived from the Skyrope calendar as follows:
- The first lunar year of a cycle begins 266 days after the Skyrope year (which usually falls in January)
- A regular lunar year has twelve months
- Months of the lunar year alternate between 30 and 29 days
- On leap years a 30-day month is added at the end of the year
- When the twelfth and last month of the lunar year falls in Pamir in a non-leap Skyrope year, it gains one day (30 days) unless a "short" leap year is about to come (that is, not in year 10 or 21 of the Skyrope 30-year cycle)
- The same principles apply to the supercycle (twelfth month gains one day in years 1 and 6 of the lunar supercycle)
The average lunar month length is 29.53054 days.
Epoch[]
The first day of year 1 in the Skyrope calendar is 5 May 2000 in the Gregorian calendar.
The first day of year 1 in the lunar calendar is 26 January 2001 (Gregorian).
Long Timespan Correction[]
Although the average year length is pretty close to the tropical year, it is not very accurate over long periods of time.
For this use case we introduce a long cycle of 3750 years, which is five 630-year cycles and one 600-year cycle. The 600-year cycle is the same as the 630-year cycle except that the supercycle comes after 570 years instead of 600.
That last supercycle has only two short leap years instead of four (years 23 and 28).
The average year length is 365.242133 days. The average Skyrope month length is 27.32158 days and the average lunar month length is 29.53058 days.
Sample Year[]
| Altai, Bukhara, Volga, Gobi | Danube | Carpathians | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 11 Apr, 9 May, 6 Jun, 4 Jul | 1 Aug | 28 Aug | ||||||||||||||||||||
| 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 | 1 | 2 | 3 | 4 | 1 | 2 | 3 | 4 | 5 | ||||||||||
| 5 | 6 | 7 | 8 | 9 | 10 | 11 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | ||
| 12 | 13 | 14 | 15 | 16 | 17 | 18 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | ||
| 19 | 20 | 21 | 22 | 23 | 24 | 25 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | ||
| 26 | 27 | 28 | 26 | 27 | 27 | |||||||||||||||||
| Nomad | Manul | Pamir | ||||||||||||||||||||
| 24 Sep | 21 Oct | 17 Nov | ||||||||||||||||||||
| 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 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 1 | |||||||||
| 7 | 8 | 9 | 10 | 11 | 12 | 13 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ||
| 14 | 15 | 16 | 17 | 18 | 19 | 20 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | ||
| 21 | 22 | 23 | 24 | 25 | 26 | 27 | 22 | 23 | 24 | 25 | 26 | 27 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | |||
| 23 | 24 | 25 | 26 | 27 | ||||||||||||||||||
| Samarkand | Taiga | Tian Shan | ||||||||||||||||||||
| 14 Dec | 10 Jan | 6 Feb | ||||||||||||||||||||
| Mo | Tu | We | Th | Fr | Sa | Su | Mo | Tu | We | Th | Fr | Sa | Su | Mo | Tu | We | Th | Fr | Sa | Su | ||
| 1 | 2 | 1 | 2 | 3 | 1 | 2 | 3 | 4 | ||||||||||||||
| 3 | 4 | 5 | 6 | 7 | 8 | 9 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | ||
| 10 | 11 | 12 | 13 | 14 | 15 | 16 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | ||
| 17 | 18 | 19 | 20 | 21 | 22 | 23 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | ||
| 24 | 25 | 26 | 27 | 25 | 26 | 27 | 26 | 27 | ||||||||||||||
| Ural | Wolf | |||||||||||||||||||||
| 5 Mar | 1 Apr | |||||||||||||||||||||
| Mo | Tu | We | Th | Fr | Sa | Su | Mo | Tu | We | Th | Fr | Sa | Su | |||||||||
| 1 | 2 | 3 | 4 | 5 | 1 | 2 | 3 | 4 | 5 | 6 | ||||||||||||
| 6 | 7 | 8 | 9 | 10 | 11 | 12 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | |||||||||
| 13 | 14 | 15 | 16 | 17 | 18 | 19 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | |||||||||
| 20 | 21 | 22 | 23 | 24 | 25 | 26 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | |||||||||
| 27 | 28 | |||||||||||||||||||||
| Month 1 | Month 2 | Month 3 | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 Jan | 31 Jan | 1 Mar | ||||||||||||||||||||
| 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 | 1 | 2 | 3 | 1 | 2 | |||||||||||||
| 6 | 7 | 8 | 9 | 10 | 11 | 12 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | ||
| 13 | 14 | 15 | 16 | 17 | 18 | 19 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | ||
| 20 | 21 | 22 | 23 | 24 | 25 | 26 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | ||
| 27 | 28 | 29 | 30 | 25 | 26 | 27 | 28 | 29 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | |||||||
| Month 4 | Month 5 | Month 6 | ||||||||||||||||||||
| 31 Mar | 29 Apr | 29 May | ||||||||||||||||||||
| 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 | 6 | 1 | 2 | 3 | 4 | ||||||
| 8 | 9 | 10 | 11 | 12 | 13 | 14 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | ||
| 15 | 16 | 17 | 18 | 19 | 20 | 21 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | ||
| 22 | 23 | 24 | 25 | 26 | 27 | 28 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | ||
| 29 | 28 | 29 | 30 | 26 | 27 | 28 | 29 | |||||||||||||||
| Month 7 | Month 8 | Month 9 | ||||||||||||||||||||
| 27 Jun | 27 Jul | 25 Aug | ||||||||||||||||||||
| Mo | Tu | We | Th | Fr | Sa | Su | Mo | Tu | We | Th | Fr | Sa | Su | Mo | Tu | We | Th | Fr | Sa | Su | ||
| 1 | 2 | 3 | 1 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | ||||||||||||
| 4 | 5 | 6 | 7 | 8 | 9 | 10 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | ||
| 11 | 12 | 13 | 14 | 15 | 16 | 17 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | ||
| 18 | 19 | 20 | 21 | 22 | 23 | 24 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | ||
| 25 | 26 | 27 | 28 | 29 | 30 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 29 | 30 | ||||||||
| Month 10 | Month 11 | Month 12 | ||||||||||||||||||||
| 24 Sep | 23 Oct | 22 Nov | ||||||||||||||||||||
| 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 | 1 | 2 | 3 | 4 | 1 | 2 | ||||||||||||
| 6 | 7 | 8 | 9 | 10 | 11 | 12 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | ||
| 13 | 14 | 15 | 16 | 17 | 18 | 19 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | ||
| 20 | 21 | 22 | 23 | 24 | 25 | 26 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | ||
| 27 | 28 | 29 | 26 | 27 | 28 | 29 | 30 | 24 | 25 | 26 | 27 | 28 | 29 | |||||||||
| Month 13 | ||||||||||||||||||||||
| 21 Dec | ||||||||||||||||||||||
| 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 | ||||||||||||||||||||||