The Annual Unit (AU), is the official Illuminatian unit used to refer to the interval of time that passes during which the Illuminatian planet completes one revolution about the planet's primary and nearest sun.
One AU equals about 216 Circadian Units, breaking convention with Illuminatia's customary division of units of measure into decimal increments. Unfortunately, the sun(s) around which the Illuminatian planet revolves were unaware of this world's eventual habitants' affinity for the number ten.
The average Illuminatian wakes up and goes to sleep 108 times in one AU. Although the direct comparison is not known for certain, it is believed that the Illuminatian AU equals approximately 126 Earth days, or just short of one third of an Earth year.
The years go by a lot faster in Illuminatia thanks to the planet's quick orbit about its most proximate sun, but Illuminatians prefer it that way. Lore passed down from generation to generation instilled the understanding that Earthlings felt the years on Earth were much too long and spoke of the longing Earthlings felt waiting for each season to come around again. Illuminatians enjoy many more circuits about their sun during an average Illuminatian human lifetime than Earthlings could have ever hoped for, which is understood to contribute to greater life satisfaction and, by extension, a longer lifespan.
When referring to a date in history or the present date, Illuminatians refer the sum of the number of AU that have passed since Lucidus survivors landed on the Illuminatian planet, or annual units AI or Anno Illuminatia. The 0th AU AI commenced on the date the first Lucidus survivors landed in Illuminatia.