Dates and Times

Days
A day on Cridhenan is the length of time it takes for it to rotate around its *barycenter (instead of on its axis, like Earth does). Since its axis is not tilted, there are 12 hours of sunlight and 12 hours of darkness every day.

* Barycenter: the point between two orbiting bodies where there is the common center of mass. Cridhenan and Giha rotate around a shared barycenter, as do the two suns - Bratis and Dimis.

Days of the Month
Unlike the concept of weeks on Earth, a Cridhenan week is directly related to astronomical factors. There is one day for each of the eight positions of the two suns when they rotate around their barycenter. This is detailed more in the next section.

The names of each day of the month (called a Pir) are as follows: 1st position: Ratio, 2nd position: Partum, 3rd position: Umeris, 4th position: Cormeum, 5th position: Pectus, 6th position: Artus, 7th position: Ventri, 8th position: Opto.

Pirs (Months)
A Pir (word that essentially means month) is measured by the rotation of Bratis (red, the larger of the two suns) and Dimis (yellow, the smaller of the two suns) around their barycenter. It takes the suns eight days to make one complete rotation, so the rotation is divided in to eight positions, dictated by where the suns are in their rotation at the start of each day.

All of this just means that there are only eight days in one Pir. At the end of a Pir, once the two suns have made one complete rotation around their barycenter, Cridhenan lines up with the next of the eight positions, and it becomes a new Pir.

Pirs are labelled by number - First Pir, Second Pir, Third Pir, and so on.

Ratio, First Pir (which is the first day of the year) is when the suns are in their first position and it is the first month of the year. At noon, as viewed from the center of the Bright Pole (in Rayiys), Bratis is large in the sky and completely obscures Dimis. About halfway through the year, on Ratio in the Fifth Pir, it is Dimis that is large and completely obscures Bratis.

So even though the days of the Pir are decided based on the position of the two suns on their rotation, the way the suns look when viewed from Cridhenan is not consistent with those days.

However, every 9.14 days, around when the number of the Pir matches the number of the position - e.g. Umeris (which is in the 3rd position) in the Third Pir - Bratis appears, from the vantage point of the center of the Bright Pole, as it does when its in its first position.

Days when Bratis is the only sun that can be seen (once every 9.14 days) are regarded as significant to different cultures of the world.

Octum
Because things are aligned so easily in sets of eight, an Octum is the name given to a span of eight years, similar to the concept of a "decade" on Earth.

Septury
On Earth, there are 10 years in a decade, and 10 decades in a century. On Cridhenan, there are 8 years in an Octum, and 9 Octums in a Septury, meaning a Septury equals 72 years.

Years
A year on Cridhenan is 64 days - the time it takes for the planet to make one revolution around the suns.

The current year in the books is 5209.