Calendar

The sky in Ailhaotnůṙ would look exceedingly strange to a denizen of Earth. There is no sun or moon, only the stars. On a cycle of 12 hours (these hours are actually about three times as long as ours, but Ailhaotnůṙ's people tend to divide everything into 12) they smoothly brighten and darken, forming the day and the night. The sky, like the world itself, is fixed upon Haotnesis, and rotates slowly around it. (You can determine how far you are from Haotnesis by accurately measuring the speed of the movement of the stars, in fact.) Each Aspect has a constellation (Called a "Sign" or lao), and each constellation is overhead for 72 days, measured in 6 12-day weeks. The stars are colored differently depending on the Aspect, and these colors are the sources of the Common Tongue names, because common people care more about the practical effects than the scriptural roles. Rather than years, time is measured in cycles and signs, with dates such as 1206.Kůṙon.4.Bůṙ for the third day of the fourth week of the sign of Rakůṙonaṙ in the 1,206th cycle.

An interesting complication is that the current sign is a localized phenomenon. For most purposes, the local calendar is used, but every locale's offset from Koṙmaṙ is kept track of for long-distance correspondence. Koṙmaṙ dates are written with a K preceding the cycle, as in K1205.Fi.5.Nul, which might be the same as the above date (The difference comes out to K+340 days, less than half a cycle). Note that in Ailhaotnůṙ, all numbers are base twelve, but for the purposes of this document, cycles are in reported in decimal.

I wrote a JavaScript widget to implement this here, so hopefully that should alleviate your confusion.

A date is formatted as: (K)Cycle.Lao.week.day:hour:twelfth:moment:tick. These terms are defined below.

Dates

Epicycles and Longer

Cycles are grouped 144 to an epicycle. (This is roughly 477 Earth years.) Rather than being numbered, epicycles are named, traditionally after great heroes of history. Which cycle an epicycle starts on is, ultimately, arbitrary, but a date was selected in prehistory and that's enough for most people. The Standard Present Period takes place in the epicycle of Hukzuṙ, a mythical smith and general.

An average lifetime can be reckoned at 18 cycles (≈60 years)

Cycles

Cycles serve a similar purpose to an Earth year, but are actually well over three times as long. ((72*12*1.4)/365.25≈3.31) They are numbered sequentially. A human denizen of Ailhaotnůṙ is what we would call an adult (18 years, rounded up) at 5 cycles and 6 lao'a. (18/((72*12*1.4)/365.25)*12≈65.22) In the Empire, legal adulthood is 6 cycles of age for citizens.

The length of a cycle presents a problem for agrarian societies, namely, the winter is longer than an entire Earth year. Food must be preserved in great quantity, and for much longer than is necessary in Earthly societies. Canning was developed fairly early in the history of humanity.

Laoä

Each Aspect has 72 days in the sky, which is almost perfectly 100 Earth days long (slightly more), called a "Sign" or Lao. Each Sign has its own characteristics, the most striking is that the stars are predominantly colored in the same way as that Aspect. Each is named in the Old Tongue with the root of the aspect's name and suffixed with "(l)ao".

The twelve signs form a zodiac, and horoscopes and astrology are very common in Ailhaotnůṙ. They are also, unlike on Earth, not complete bunk.

In Order:

Iron (Listao)

The stars are dim and rusty grey in color. Though still rather cold, the sign of Iron marks the end of Dusk, and the beginning of "spring".

Glass (Kaṙlao)

The white stars form constellations of perfect geometric order, dispelling the last frosts in temperate climates.

Silver (Salao)

The stars brighten and twinkle. The temperature climbs steadily.

Gold (Kuṙonlao)

The stars take on a golden cast, their light invigorating beast and plant alike.

Red (Kofao)

The stars burn with fiery intensity, casting enough light even during the night to keep away the chill. During this sign, people in warmer climates often adopt a "nocturnal" lifestyle to minimize heat stroke.

Blue (Sulao)

The stars fade significantly, their somber blue light rarely seen through the clouds of the monsoons and thunderstorms.

Green (Vollilao)

The stars are multicolored, but more spectacularly, aurorae paint the sky both day and night, in breathtaking colors, predominantly greens, though blues, oranges, and even bright pinks are not uncommon. Unlike the other signs, which are generally very consistent, the onset and end of Volilao have been recorded to be as much as a week off from the calendar dates.

Grey (Jafao)

The stars once again lose their color, this time marking the end of the warm season. Their feeble light no longer nurtures the crops.

Purple (Lalao)

The stars become colored in deep purples, making good color vision difficult even during the day. In temperate climates, the first frosts generally occur by halfway through this sign.

Black (Filao)

The depth of winter, not even a tenth of the stars present in the other signs grace the skies with their presence. Very few places remain unfrosted at night.

White (Nalao)

The stars of Nalao are brilliantly white, though lifelessly chilly.

Spirit (Islao)

During this sign, the daily change of the brightness of the stars is mostly muted, and the entire 72 days is spent in twilight. Only those with clocks are ever sure of how far through they are. The temperature is generally comfortable, but food crops do not grow in the absence of the daily cycle of brightness. The duration of this sign is a holiday known as "Dusk", the celebration of the end of the cycle. During this time, gifts of charity are given every Fourth Rest, and the working days are marked by a partial fast.

Weeks

A week is 12 days long, which can be numbered (1-10 in base 12), but they are often named instead. There are six weeks in a lao. The days are named by analogy with the stages of life:

Nitůtkat (Ni)

First Rest day

Saṙkat (Saṙ)

Babe day

Bůṙkat (Bůṙ)

Child day

Ůṙfkat (Ůṙf)

Adolescent day

Ripkat (Rip)

Young Adult day

Hatůtkat (Ha)

Second Rest day

Jutůtkat (Ju)

Third Rest day

Zeddakat (Zed)

Adult day

Foṙtkat (Foṙt)

Old Adult (a common term used to refer to people roughly 37-50 years (11-15 cycles) old, no English equivalent) day

Saokat (Sao)

Elder day

Nulkat (Nul)

Death day

Ketůtkat (Ke)

Fourth Rest day

Even-numbered rest days (second, fourth) are just shorter work days, rather than total rest days.

Times

A day is divided into 12 hours (With a day of 24*1.4=33.6 earth hours, each hour is 168 minutes) starting from 'dawn' (halfway between noon and midnight), each of which is divided into twelfths. (14 min) Each of these is divided into 144 moments, (5.83 sec) and most clocks tick 12 times in a moment, giving rise to the smallest unit in common use, the tick (0.4861 sec). A time is formatted as :3::: for noon, or :2:B:BB:B for one tick before noon. A full date and time reads "K1205.Fi.5.Saṙ:2:B:BB:B" for one tick before noon on the Babe of the fifth week of Filao in the cycle 1,205, as measured in Koṙmaṙ. For a zero time, one may leave the space between the colons blank. (":8::5" for 5 moments after the 8th hour). A less precise time is denoted by leaving off colons, as in :6:0 for "within a twelfth of dusk". Moments and ticks are almost never written down, and even marking twelfths is considered needlessly precise in most cases.