Naiparkuan Calendar

Naiparkuan Calendar is the lunisolar calendar used in Naiparku.

Background
According to Coloria Planetary Physics, a lunar cycle (the time it takes for Coloria to orbit the Gas Giant completely) contains 32.6583 days, while a solar year (the time it takes for the Gas Giant to orbit the sun completely) contains 1964.3333 days. Thus, a solar year would contain 60 complete lunar cycles plus 4.8353 days.

Naiparkuan Calendar is constructed based on this information. It has 60 lunar months (shumuwih, "onset of eclipse and end of eclipse") in a lunar year (hwokse, from "sixty"), 20 32-day months and 40 33-day months, which amounts to 1960 days (4.3333 days behind a solar year).

Names of months
The names of the months in a year are formed by the combination of the 12 "element words" (zwokoduhye) and the numbers 1-5 (vyet, adis, kom, nodo, pira), resulting in a 60-year cycle. The element words are:


 * Bowanar ("imbuement") [坤]
 * Nahi ("agility") [奈]
 * Kosdu ("far away land") [斯]
 * Urwo ("creation, conception") [姆]
 * Byosi ("downward place") [亞]
 * Vyar ("moralness") [德]
 * Charachar ("victory") [克]
 * Bana ("pepper vine") [葛]
 * Osoyur ("descent") [洛]
 * Huse ("tree") [森]
 * Hatoko ("rattan fiber") [絲]
 * Veyora ("veyora") [薇]

Intercalation
In an ideal lunisolar calendar where the difference between a lunar year and a solar year is minimized, leap months would be inserted with the following scheme:
 * Every 8 years, one leap month of 34 days added (0.6664 days behind)
 * Every 8*50=400 years, one additional leap month of 33 days added (0.32 days behind)
 * Every 8*50*100=40000 years, one additional leap month of 32 days added (0 days ahead, but not implemented for now)

This is more or less the system used in the Yanyuhoshe region. However, in most other regions, due to the Naiparkuan's preference for "easily manageable" numbers like 6 or 9, as well as the fact that seasons following the solar cycle is less important in the tropics, the leap months are inserted with the following scheme:


 * Every 9 years, one leap month of 32 days added (6.9997 days behind)
 * Every 9*6=54 years, one additional leap month of 32 days added (9.9982 days behind)
 * Every 9*6*9=486 years, 3 additional leap month of 32 days added; added in the 3rd, 6th and 9th 54-year cycle (6.0162 days ahead)
 * Every 9*6*9*6=2916 years, 1 leap month of 32 days not added (4.0972 days ahead, but not yet implemented)

Eclipse
The onset of the eclipse (shumu) falls on variable time of the day over the months, but returns to the same time after a two-year (120 months) cycle (churwadase). However, the day of the eclipse (gwoshumu, "night of the onset of the eclipse") as a whole "drifts" earlier one to two days every cycle.

In a two-year cycle, 14 months (months 19, 22, 25, 28, 31; 60, 63, 66, 69; 100, 103, 106, 109, 112) have an eclipse that completely cover the daytime of one day, resulting in a 36-hour long night (uwihchin, "(to reach) the end of the eclipse over/across (another day)").

More detailed information of the Naiparkuan Calendar can be found here.