The Neptunian calendar is the calendar used by the Neptunian Culture. It is oriented around the solar year, and the change in light and darkness in particular. Neptunians tend to be very phototropic, so the difference in light between winter and summer has a large effect, especially on a planet with high axial tilt like Halcyon.
The Neptunian approach to dates is as relaxed as the rest of their society. Indeed, the divisions of the year seem to mainly serve to schedule things like sun-bathing (tracking day length) and surfing (tracking moon phases for tides).
Neptunians see the progression of the year as a wave of sunlight breaking over them, high (bright) in the summer, and low (darker) in the winter. Indeed, the formal name of the calendar is year#wave (The "Wave of the Year"), and the seasons are named accordingly:
- Rising (Spring)
- Cresting (Summer)
- Breaking (Autumn)
- Resting (Winter)
Each season is then broken into two equal-sized ‘turns’, the Full turn, which contains the solstice/equinox day and the Cross turn, which contains the following cross-quarter day.
- Full Rising
- Crest Rising
- Full Cresting
- Break Cresting
- Full Breaking
- Rest Breaking
- Full Resting
- Rise Resting
Dividing a Year
While the Wave of the Year is in most common use on Halcyon, the calendar actually predates its founding as was constructed to be applied to a year of any length, as long as it has seasons. The Neptunian Calendar is adapted to any year length by dividing the year into 8 divisions as evenly as possible, and then setting aside the rest of the time as intercalary days in the middle of Full Resting, centered around the winter solstice itself. This time is set aside as Glowtide, a special set of celebratory days not counted as part of the regular year. To ensure that the intercalary days are perfectly centered int he middle of Full Resting, the middle-day of that turn (what would be the solstice day if the number of days evenly divided into eight) is included in Glowtide, meaning Full Resting technically contains one day less than the other turns.
Halcyon’s orbit was tuned to make the Neptunian calendar easy to apply, while keeping a year very close to Earth standard. The Neptunian year is exactly 364 days long, allowing for 45-day turns (44 for Full Resting), and 5 days of Glowtide, which is one full cycle of Ceyx. Since the number of days is one short of divisible by five, this also creates a five-year precession in the phases of Ceyx, which ensures that high and low tides vary from year to year.
Mapping this to the Gregorian Year is quite similar to the Halcyonian year. Again, turns are 45 days long, with one reserved from Full Resting, and the extra time goes into Glowtide. Glowtide thus lasts six days in most years, and 7 days whenever a leap day needs to be added. The leap day is added the year BEFORE the leap-day in the Gregorian calendar, so that the calendars only misalign for 2 months rather than 10.
For standard years, the Neptunian calendar lines up with the Gregorian one as follows. In the year immediately preceding a Gregorian leap year, Glowtide lasts one more day, so the resumption of Full Resting and the start of Rise Resting are one day later.
- Rise Resting starts January 16
- Full Rising starts March 1
- Crest Rising starts April 15
- Full Cresting starts May 30
- Break Cresting starts July 14
- Full Breaking starts August 28
- Rest Breaking starts October 12
- Full Resting starts November 26
- Glowtide starts December 21
- Full Resting resumes December 26
Dividing a Turn
The specific divisions inside a turn vary from one calendar implementation to another, but the divisions for the Halcyonian and Earth calendars are the same, and fairly simple. Each turn is broken up into ‘early’, ‘middle’, and ‘late’ sections, called ‘swings’, of 15 days each. Each of these can then be broken up into early/middle/late again, for 5-day week-equivalents, known as ‘moons’ (or sometimes long-tides) since they have the same cycle as Ceyx. Many Neptunians don’t bother to be so precise, though.
When these specific days are written down, they’re written down using a numeric/symbolic system. Year, season, and turn are written numerically, and the rest are using symbols of half-circles and circles, denoting the position in the turn, division, and moon.
Example, for 12/05/2013: 8334 2 1 (0> Year: 8334 NC Season: Resting 2 Turn: Deep 1 Swing: Early ( Moon: Mid 0 Day: 5 >
Early, mid, and late are marked by (, 0, and ), respectively. Days are similar, with 0 marking the middle day of a moon, and < and > added at the beginning and end to fill out the five.
If someone wanted to say the whole date out loud, it’d be basically read in reverse direction:
5 Mid Early Deep Resting, 8334
Glowtide, lasting a single moon, just replaces the season, turn, swing, and moon sections, and is notated as 0, making Deep Glowtide of the same year written out as 8334 0 0