Concalendar
From KneeQuickie
A concalendar is a calendar used within a fictional culture. Unlike constructed languages, concalendars are very rarely, perhaps never, created as an art form in themselves; they almost always go with a conworld setting or a conlang.
Basically, a calendar consists of a system for keeping track of time, specifically in the long-term. The smallest unit in a calendar is usually the day, which comprises successively larger units such as months and years.

