While many regions and cultures have their own form of timekeeping, the Ershadi methods remain in widespread use.
The Ershadi calendar has 12 months with 25 days each, leading to a year of 300 days, the (approximate) time it takes for the world of Tellaria to orbit its sun. The months are focused around 4 seasons, with the beginning of each season coinciding with the equinox/solstice.
Spring months: Vanitia, Illumia, Khastio
Summer months: Tylio, Laegia, Molario
Autumn months: Caebrio, Prisio, Sunio
Winter months: Selinia, Sojio, Baometia
There are five days in each week: Aeridi, Aquadi, Terradi, Ignidi, and Requiedi.
Requiedi is considered the “weekend”, and workers will typically work four days and have Requiedi off.
Many cultures celebrate their own festivals, but these four festivals correspond to the days of the equinox or solstice, marking the days of each season, as well as the start of a new month.
Spring equinox: beginning of Blossom, marked by the Feast of Flowers
Summer solstice: beginning of Highsun, marked by the Feast of Innovation
Autumn equinox: beginning of Harvest, marked by the Feast of Fruition
Winter solstice: beginning of Frost, marked by the Feast of Concord
The establishment of “year 0” and numbering years from a set date was created by scholar Leyli Tarrokh, during the height of the Ershadi empire. Prior to that point, most cultures kept track of years by counting from the beginning of the current monarch's reign (e.g., “the 5th year of King So-and-so”).
The year 0 EE is designated from the beginning of the rule of the first Ershadi emperor, Sadaf Karimi. Dates before this are designated with negative numbers, e.g., -45 EE.
The empire itself lasted from 0 to 348 EE, then splintered off into separate kingdoms and dominions. The current year under this system (before our adventure starts, that is) is 477 EE.
The world of Tellaria is orbited by two moons, one of which is larger and closer (similar to Earth's moon), and the other smaller and further away. Tidal forces are primarily dominated by the larger moon.
The larger moon orbits the planet every 25 days (from which comes the length of the “moonth”), and the smaller moon has a more erratic orbit of between 38-46 days.
While the Ershadi empire had much influence over the systems of timekeeping used, many cultural traditions and myths exist about the moons of Tellaria. For example, in Encorin, the moons are called the Lovers; the myth is that they were once one, but the gods pushed them apart, and so they cast their light in order to find each other once again. In Caedyrn, the larger moon is the Giver, and the smaller the Taker; when the two moons are close together in the sky, this is a sign of good fortune and peace; while when they are far apart, they are angry at each other, and this is a sign of strife.