Updated Athasian Moon Calendar

4125 days of adventure!
One complete Endlean cycle of a Kings Age!
Over 500 days to celebrate about!

Sometimes I do stuff.

I’ve updated my Athasian Moon Calendar.
This calendar follows the same lunar convention used on The Merchant Calendar program. 33 days for Ral. 125 days for Guthay.

The full calendar is 11 pages. One page for each year in the Endlean cycle and then it repeats.

I added a few graphics for the Star Sign that corresponds to the month. (Hello, Ivory Triangle.)

I Added the name of the Star Sign and the name of the month used in 4e. (In case that is your thing…)

I Added a ton of holidays and festivals for each city-state, some races, and important dates for elemental and para-elemental forces that may be more powerful during specific times of the year and would be important to a cleric.
Some of these I made up, but many of them are based on what I could find in the various books.

I also include a blank calendar with no lunar info event.

I also added a list of tables to quickly find days when moons are new, full, conjunct, etc. A table of a full Kings Age (77 years) so you can easily see what years correspond to which Endlean and Seofean cycle. FY 1 starts in Priest Defiance of KA 190.

And a table for selecting a random day, week, or month.

Check it out here: Moons of Athas: Updated Athasian Moon Calendar


Awesome! Thank you Rovewin.


This is great! Your whole website is great.

I feel that describing realistic moon motions and starscapes adds a lot of drama and flair to the setting.
I get a lot of information from your materials, but still feel generally lacking in knowledge about how such things work. Do you have a resource where I could learn basics?

Also, have you got examples where you’ve actually used elements from this moon calendar in gameplay that you would be willing to share? I’m talking about how you as GM would give info or describe situations to the players.


To be honest I haven’t had a chance to use this calendar in game play as I only get to play in Dark Sun about once in an Endlean cycle,or maybe once in a Seofean cycle. :wink:

I’d imagine it would be useful for games that are long campaigns where placing dates on events are meaningful. Or for a game that has an in game time constraint of a few weeks, few months or a year. Not so useful for hack and slash type games. But just putting all the info together spawned all kinds of ideas. For what is missing in DS.

I have a love of science, astronomy, and Dark Sun. And I have studied calendar systems in the past. The subject matter also forced me to do a dive into ancient astrology to get some ideas. I have an engineering background so I can follow the physics and work the math. Putting this stuff into Excel comes easy and enjoyable for me. Most of the stuff I cover is basic astronomy but I use Wikipedia and YouTube for where my knowledge lacks. One good resource is timeanddate.com which has some useful info as well. Like this page on phases of the moon.


I was using a calendar of my own design, for my long campaign, but I will be using this one in the future. This one is more detailed.

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If you have any recommendations to add to it or things that need to be fixed let me know.

I made it so it syncs up with the Merchant Calendar program so you can use the two together.


I’m working on another calendar similar to this but Draj themed. It will still follow the patterns of the moons in this one. However, it largely ignores the calendar stuff from CSoD but will sync up between the program and this one. until then, I have this calendar that follows CSoD


Thanks so much for the tips. Going to read them.

I’ll be using the material for a new campaign I’m starting up. Mostly going to be doing that to mark in game time passing more realistically, but will also be using it tied to events and rituals.