Infernal calendar

The Infernal calendar (Fengese: 炎歷, : Yánlì, : Houreki) is the dominant calendar and system of timekeeping used in the Occident and wider Pyrosphere - traditionally corresponding to the cultural sphere influenced by the occidental and Fengese religion of Infernalism. Alongside its oriental counterpart, the Getic calendar, the two calendars are the pre-eminent calendars in use across Tellurus. Being a, it combines elements of a (corresponds to the  in the long term) and  (uses  for months) to reckon the lengths of its years and months. The calendar was first instituted by the Apostle Guashi some time in the 1000s BCE during the reign of the semi-mythical Pyrotic Matriarchy, and has remained the primary calendar for Infernalism since then, only with minor modifications following greater advances in technology and understanding of astronomical phenomena.

Years
The Infernal year (年, nián) is 360 days long. Given that the mean duration of a tropical year is 365.24219 days, the Infernal calendar advances approximately five and a half days earlier each year. This deviation is accounted for with the introduction of an week lasting ten days (as is Infernal standard) every two years (360 x 2 + 10 = 730 days; compared with the tropical mean of 365.24219 x 2 = 730.48438 days). As for the unaccounted decimal day left in every year (0.24219 days), this is resolved by the inclusion of an additional day every four years (1 / 4 = 0.25 days) - the remaining rounding error is accounted for with the skipping of the quadrennial 371-day leap year, announced at the pleasure of the Prophetic Order for Celestial Observation.

Simplified, there can be three different lengths of an Infernal year:
 * A small year lasting 360 days. This is the "normal year", matching the four-harmony sequence of the base Infernal year.
 * A medium year lasting 370 days. This occurs every second year, except for the fourth year when the 371-day great year occurs.
 * A great year lasting 371 days. This occurs every fourth year, but may rarely be skipped and rendered as a 370-day medium year.

The of the Infernal calendar is set at the purported day of the Transcension of Yanshizu, believed to have occurred at the end of 1090 BCE. Similarly to the Getic calendar, there is no in the Infernalist calendar: the year immediately after Yanshizu's transcension is year 1, while the year before is -1. To reduce confusion with the Getic year, years before and after transcension are labeled as Smija Riqis (SR, "year of darkness") and Smija Liuhaþ (SL, "year of light") respectively, imitating the Getic SF standard; this manner of year labelling is a foreign invention and is not done natively however (see ). Conversion between Infernal and Getic years is commonly done by adding 1089 to the Getic year: for example, 2024 SF is 3113 SL.

Months
The Infernal month (月, yuè) lasts exactly 30 days long, consisting of three 10-day Infernal weeks. Three months make up one harmony (和, hé), while twelve months (or four harmonies) make up one year. The 90-day length of a harmony is comparable to the period of time taken for a to occur between Tellurus' two moons: the nearer Ersa (whose orbital period is approximately 30 days) and farther Eos (whose orbital period is approximately 45 days). The Infernal calendar places no special importance on months, using it merely as a practical timekeeping device which groups together the more significant weeks - the arbitrary 30-day length of a month is loosely based on the length of the 29.53059-day period needed for Ersa to complete a, historically useful for agriculture timekeeping but now mostly obsolete outside its use in comparisons with Getic months. Greater emphasis is placed on the 90-day harmonies as they are used to approximate the durations of the four seasons. Reflecting this, the universal Infernal calendar names harmonies but only numbers months, though more unofficial versions may have special month names differing from region to region.

When leap years (of either 370 or 371 days) occur, the additional days are added onto the final month of the year. This intercalary week of either 10 or 11 days is known as the Serene Week and is considered a time of religious observance and contemplation, especially as it occurs right after the Montane Day: the anniversary of Yanshizu's transcension on the final day of the year.

Days of the week
The Infernal week (旬, xún) is ten days long, defined as such because Infernalists are obliged to gather at their local pyres every tenth day to contemplate and conduct religious rituals. This "communal day" (集日, jírì) is the official across the Pyrosphere, considered a day of communal prayer and rest, during which a person could receive bestowment and dissociate themselves from temporal duties and dedicate time to the cultivation of their inner light. Numerous countries in the Pyrosphere adopt both the ninth and tenth day as two-day weekends in emulation of oriental Saturday and Sunday weekends, though this is arguably untraditional - more fundamentalist countries like Mantaly institute single-day weekends based on this belief. There are nine weeks and unique names for each, rotating every harmony instead of month. The weeks are named after aspects of Brilliance and Oblivion: the first four are named after oblivious concepts while the next five are named after brilliant concepts, symbolizing the blissful triumph of Brilliance over Oblivion as foretold in the Prophecy of Obliteration.

The tenth week is intercalary and 10 or 11 days long, occurring depending on the Infernal leap year.

The Infernal day (日 rì) is 24 hours (時 shí) long, each hour being 60 minutes (分 fēn) and each minute being 60 seconds (秒 miǎo), similarly to oriental standard. All of these are multiples of 12, assigned units the from used in traditional Fengese timekeeping, though the use of plain numbers is more common in modern times. Traditionally as well, days in Fengjiang began at sunrise and ended at the next sunrise, creating seasonal variation in the length of days - the 24-hour convention which begins at midnight is a mostly oriental borrowing. Beyond the mandated communal day for prayer, specified hours of every day are also reserved for worship, generally at dawn, high noon, and sunset.

Expressing dates
The native method of expressing Infernal dates starts from the largest unit and ends with the smallest: from the year, then to the harmony, then the week and lastly the day. Months are generally not included as they are largely redundant with the harmonies and weeks.