Days and Weeks
This is identical to our world. A week is made of 7 days, Monday to Sunday. The only difference is that there are no months names (see below).
In Aravorn there are four seasons, named: "Hibernia" (Winter), "Floreas" (Spring), "Solaria" (Summer), "Arboris" (Fall). Each one lasts 100 days. So there aren't separate months names, but a date could be for example: day 75, Solaria or day 99 Arboris and so on.
The year 0 is when Grimoire, the most ancient human town, was founded. Other races might have a different way of counting years, but most of them have adopted that system too.