Though you may not encounter much about the calendar at use in the land of Arelatha, it is nonetheless at play behind the scenes, helping orchestrate everyone's lives. To keep matters simple for you, the reader, so that you don't have to "interpret" everything to make sense of it, I have not bothered with renaming units of time. There are still minutes, weeks, and such, and there is no need for you to reimagine what that means. Also, seasons are normal with colder temps toward the poles and heat along the equator.
There is one sun, around which the world of Kreth revolves in the space of 336 days (12 months of 28 days). Each month is demarcated by the single moon's orbit around Kreth, being "new" on the first of each month and full on the 15th. Days are 24 hours long, again, to keep things simple for you. Hours are 60 minutes and minutes are 60 seconds. But that's really all the boring stuff that only an astronomer would care about.
The universal calendar marks time from the end of the "Annihilation," that devastating period of time when the Ancient Five each vied for supreme rule over the others. These five sons of Vaeroloth might have gone on to destroy the entire world in their fight for dominance. But the Maker sent twelve avatars, his light-bearers, to throw the Ancient Five into confusion, to teach Creation how to resist and withstand evil, and to mentor cassocks that would continue to instruct generations of people. With the sending of these avatars, a new age dawned and the world was reborn. This begins Year 1 of the current calendar.
Each month is named after the dominant constellation in the sky during the month. Here they are, with the usual season and common holidays. Note that each of the twelve primary sects has a religious holiday in one of the months (italicized), and there are a few "universal" holidays celebrated across the whole land. In addition, each nation adds to this list its own selection of commemorative days.
Anthozoa (early spring)
1st - Commencement: The House of Order begins each new year with a day of solemn oath-taking, vows to better align one's life and habits according to the perfect order of the Maker's design.
10th - Rite of Spring: The Arthouse sets aside a day to show special affection to one’s dearest love. Typically this means exquisite dinners, finely crafted art, poems or songs, and costly gifts exchanged. What began as a day to “do something nice” for your beloved has turned into an extravagant display of largesse. Many children are born in the month of Capra…
17th - Truce of Prazios: Marks the official signing of the truce that ended the Wars of Attrition, heralding "the beginning of a new era of peace across Arelatha." This hasn't quite happened, but most nations celebrate the ending of the wars anyway. The truce was signed in the town of Prazios in the Border Lands, where, ironically, remnants of the wars still continue.
Celestine (late spring)
21st - Pavesine: A day dedicated by the Church of Stewards to the planting of trees, particularly in large quantities. Children will sometimes plant only a single tree in honor of a deceased family member.
Tefia (early summer)
8th-14th - Tournament of Champions: A weeklong set of tournaments established by the Hall of Champions for nearly every conceivable engagement: running, lifting, jumping, throwing, shooting, swimming, and a growing number of "trivial" things that people take quite seriously--cup stacking, pie eating, log rolling, ring tossing, mule driving, and on and on...the list is endless.
14th-16th - Festival of Lights: On the longest days of the year, when the moon is full, it is said the land is bathed in continual light. The Solarium celebrates this three-day period by lighting floating lanterns (both air and water) and making various displays of magical light. Healing services are deeply discounted or offered freely.
Alopex (late summer)
1st - Tarchannen: The darkest of nights, a time when it is said that the Void touches the earth. Untethered dead have a horrible tendency to rise and roam the land on this night.
2nd - Reclamation: The Bastion of Faith is particularly active on the day following Tarchannen, cleansing the land of any undead that happened to awaken on the previous night. They have done this for so long and with such passion that it has become a sacred holiday.
25th - The Ides of Summer: Derisively known as "Loafer's Day," this is a day off from the work of summer, ostensibly in honor of the Summer Queen, who is usually chosen through local pageantry. This day off, however, has transformed into a day filled with festivities and indulgences such that many folks now need a day off from the "day off."
Arini (early fall)
4th - Introspection: Originally intended to be a day of self-reflection for personal betterment, the day has become increasingly self-indulgent. Instead of taking a day to improve one's character, members of the Liberty House regularly spends the day bestowing lavish pleasures upon themselves.
9th-13th - The Kelione: In what is typically the most pleasant time of year, the Open Path sets aside these five days particularly for the launching of extended journeys and discovery.
Phoca (late fall)
22nd - Day of Solemnity: For the Celebration House, the idea of a day of solemnity right before the Brewer's Consortium is pretty funny. The day is filled with practical jokes, pranks, and general mischief.
23rd-27th - Brewer's Consortium: A nearly universal four-day convocation of harvest festivities, centered around the tasting and judging of local brews. A few nations do not allow this festival, owing to the fact that it usually produces a bunch of drunken sots.
Fregata (early winter)
15th - Odhasaim ("Hasam" for short): A sacred day to the Grove when, under the full moon, the borders with the spirit world grow thin. Anyone raised to life on this day receives a special blessing. There's also a danger of vengeful evil spirits making contact with the material world.
11th-14th - The Days of Jubilee: Three days set aside for the righting of wrongs. In many lands, pardons are granted or sentences commuted. Relationships are mended (and some fences) and thankful hearts abound.
15th-16th - The Days of Remembrance: Following Jubilee, the Sanctum continues its observances with a pair of days set aside to remember loved ones, particularly extended family. Feast are frequent and family reunions common.
Pterois (late winter)
15th - Night of the Dead: The Nexus remembers under a full moon the passing of those who died during the year, offering prayers for them and giving token gifts to the families left behind. Bonfires from collected dead branches send showers of sparks into the night sky, symbolizing the souls of the dead going up to the Maker.
24th-28th - Midwinter: While technically the end of winter, per the calendar, the cold is hardly gone, and it sure feels like mid-winter. Regardless of temperature, these last days of the year are a time to reflect and to prepare for the year to come. Deeds of kindness are commonplace, especially toward the less fortunate, and gifts are often exchanged.
As might be expected, the Zenith of Orthodoxy does not have its own holiday but rather celebrates them all. Each sect of Maker worship also observes a wide variety of worship days; some practice weekly, while others monthly or quarterly. This disparity means that there is no universal "day of worship." Work weeks, therefore, are typically all seven days except when holidays or worship is being observed.