The Octalendar is a perpetual leap week calendar design that divides the year into 8 months, called a spoke, of exactly 6 or 7 weeks, alternating 7:6. That means, every odd spoke has 49 days and every even spoke has 42 days, except for the last, eighth one in leap years when it has 49 days instead.
The date format is ISO-like ±YYYY-S-W-D. All usual date conventions comply with ISO 8601, i.e. weeks start on Monday and the leap week depends on the Gregorian leap rule and year count. Among other things this means, the year number, CCYY or YYYY, is always the same as in ISO week date and the day of the week, D, is the same in Octalendar and Gregorian.
Today is 2024-8-6-5 in Octalendar and 2024-09-27 = 2024-W39-5 by ISO 8601. If more disambiguation from Gregorian dates is required, the lowercase letter o can be added after the year; hyphens become optional then: 2024o865.
Two adjacent spokes can be grouped to form a quarter or season of 13 weeks. Only the final quarter spans 14 weeks once per 5 to 6 years.
The name spoke for its months is inspired by the Celtic Wheel of the Year which also divides the year into eight parts, but at annual astronomic events. Lacking any better source, their names are also derived from the Celtic festival seasons.
Cal7 also has months with 7 weeks, but alternates them with ones of 8 weeks (8:7), totalling in just 7 months.
| Week | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 13mon | Janon | Febron | Marchon | Apron | Mayon | Junion | Extron | Julon | Augon | Septon | Octon | Novon | Decon † | ||||||||||||||||||||||||||||||||||||||||
| 5:4:4 | Janaire | Febraire | Marchose | Aprilose | Mayose | Junal | Julial | Augial | Septidor | Octidor | Novidor | Decaire † | |||||||||||||||||||||||||||||||||||||||||
| 4:5:4 | Janose | Febrose | Aprial | Mayal | Julidor | Augidor | Octaire | Novaire | |||||||||||||||||||||||||||||||||||||||||||||
| 4:4:5 | Febral | Marchal | Maydor | Junidor | Augaire | Septaire | Novose | Decose † | |||||||||||||||||||||||||||||||||||||||||||||
| Quarter | quart 1 | quart 2 | quart 3 | quart 4 † | |||||||||||||||||||||||||||||||||||||||||||||||||
| 7:6 | Bol | Sar | Tan | Lit | Nas | Mon | Sam | Yul † | |||||||||||||||||||||||||||||||||||||||||||||
| 4:5* | Janose | Febrose | Marchose | Aprilose | Mayose | Junal | Julidor | Augidor | Septidor | Octidor | Novidor | Decaire † | |||||||||||||||||||||||||||||||||||||||||
| 9:9:8 | sester 1 | sester 2 | sester 3 | sester 4 | sester 5 | sester 6 † | |||||||||||||||||||||||||||||||||||||||||||||||
| 5:5:6:5 | Primoth | Secoth | Tertoth | Quaroth | Quintoth | Sixtoth | Septoth | Octoth | Novoth | Decoth † | |||||||||||||||||||||||||||||||||||||||||||
| 10:11 | quinter 1 | quinter 2 | quinter 3 | quinter 4 | quinter 5 † | ||||||||||||||||||||||||||||||||||||||||||||||||
| 8:7 | Monmonth | Tuesmonth | Wednesmonth | Thursmonth | Frimonth | Saturmonth | Sunmonth † | ||||||||||||||||||||||||||||||||||||||||||||||
| Terms | Spring semester | Summer break | Fall semester | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Winter semester | Spring break | Summer semester | Fall break | Winter semester | |||||||||||||||||||||||||||||||||||||||||||||||||
| Epiphany/Hilary trimester | Trinity trimester | Summer break | Michaelmas trimester | ||||||||||||||||||||||||||||||||||||||||||||||||||