There are many different calendars used by different cultures and groups in the world and over history. Some are based on the solar cycle; some on the lunar cycle. The Calendar Wiki has over 200 articles "about calendars - historical ones, new ones, and discussions about them: for the scientist, astronomer and the calendar enthusiast."

Lightly active wiki
This wiki is active, but at a fairly "light" level.
The low level of activity or smaller size of this wiki may be because it's new. Or perhaps it's an older wiki that's been growing slowly over time. Either way, it could use additional contributors, would you like to help?