Octosol

A perpetual, circular, solar calendar for the northern hemisphere 🌞 Inspired by the 'Wheel of the Year' 🌱 🍎 🍂 ❄ SVG via Inkscape ✒

Should be

• simple
• 'perpetual' (i.e. I don't have to make an updated version every year)
• circular (to remind us of the cyclical nature of the year)
• oriented around the solar cycle (i.e. the earth orbiting the sun every 365.242199 days with an axial tilt oscillating between 22.1° and 24.5° every 41,000 years ;p)

Should feature

• 4 seasons
  • winter
  • spring
  • summer
  • autumn
• 8 solar/thermal intervals including (approximate) calendar date, symbol, common/special name
  • 4 quarter days
    • winter solstice
    • spring equinox
    • summer solstice
    • autumn equinox
  • 4 cross-quarter days
    • 1st (Imbolc)
    • 2nd (Beltane)
    • 3rd (Lughnasadh)
    • 4th (Samhuin)
• 12 months of the year

Should not feature

• Zodiac signs
• daylight/saving times
• days of week
• weeks
• moon events (although nice, not quite as important and a lot more complexity)

Background

For some time I've wanted to better celebrate the rhythms of the earth, sun and moon—the moon orbiting the earth and the earth spinning on its tilted axis while orbiting the sun. I want to remember that these celestial motions are happening, and I'm a tiny part of them. I find it easy to forget, and often imagine the universe revolves around me.

The solstices and equinoxes ('quarter days') are the most obvious obvious solar events of the year. They've been celebrated by all kinds of cultures through history, and Christianity co-opted some going forward: Christmas is pretty much set on the winter solstice. But the solstices and equinoxes aren't the only ones that have been celebrated

A bunch of friends I met in Edinburgh introduced me to Beltane, a Gaelic celebration for the beginning of Summer, marked on the last of April/first of May. It seems the festival was largely extinguished by the 'civilizing' of the Gaels and the slow-drip of modernization, but the lively revival by the Edinburgh group in 1988 continues to this day. Beltane doesn't occur on a solstice or equinox, but directly between the Spring equinox and Summer solstice, one of four so-called 'cross-quarter days'.

The cross-quarter days seem to have been as big a deal as the quarter days. Perhaps not coincidentally, the seasonal lag (the time it takes for the solar radiation to fully affect the air temperature) for much of Europe is roughly 6 weeks! As such the cross-quarter days are essentially the thermal equivalent of the solar solstices/equinoxes, shifted forward a half-interval. The solstices, equinoxes and cross-quarter days come to 8, equally-spaced solar events in the year.

The months of the year are a relatively arbitrary, relatively modern (Roman) mathematical invention to reconcile the difference between the day (earth spinning) and the year (earth orbiting sun). The cross-/quarter days, on the other hand are directly related to the seasons and grounded in the physical realities of heat and light—the literal power sources that keep life-on-earth going.

When I was looking for calendars, I didn't find anything I was quite looking for. I generally found more technical calendars when searching for 'solar calendar' or 'circular calenda', with lots of details about days of the week etc. These were mor in the direction of year planners, which is way more than I'm interested in. When searching for 'wheel of the year', I entered Wiccan-world! Many beautiful diagrams, but often lost in details I'm not interested in: runes, tree-types, zodiac signs, etc. In any case, I couldn't find any source files to easily make adaptations from.

Other relevant projects/things

• The diagram for the Wikipedia wheel of the year article. (Very simple, lacks seasonal/month info)
• 'mycircularcalendar', main page, circular, commercial calendar, with a nice daylight visualization. (No emphasis on (cross-)quarter days, lots of detail, unavailable)
• strawdog circular calendar, main page, source. This is a very detailed circular calendar from a Montreal hacklab. (Montreal specific, open-source, significant dependencies, a lot of detail and not an emphasis on (c-)q days.)
• timeanddate.com have nice stats on average temperature and insolation
• 'Solar wheel of the year', source, is a very simple calculator for the (cross-)quarter days in every locale! I'm not 100% sure how accurate the math is, but it seems like the best resource I've come across so far. The visual diagram at bottom is lacking.
• 'The Eight Season Year', source, another (c-)q days calculator... but not very clear visually (although beautiful). Mostly corresponds with the above calculator, but not entirely.
• Round calendar by Robert Alcock, main page, a calendar with the explicit intention of reconnecting with natural cycles! Includes the (c-)q days more or less, and has an insolation indicator. (no source, not updated since 2017, a lot of visual info)
• Celtic Ogham Year Wheel by Yuri Leitch, main page. A good example of a beutiful but too esoteric diagram.