Hello, Bay12Forums and fellow Dwarf Fortress designers, Resmisal here, long time fan and no time forum goer here! Congratulations to the official release and may there be more steam in your mist engines.
I'm here to present a simple mathematical model for a lunisolar calendar to liven up the experience during full moons as well in preparation of an equally simple eclipse cycle. You see, Armok's the Dwarven calendar counts neatly and exactly 336 (three hundred thirty six) days, and this will take a huge load off any shoulder that wishes to introduce solar and lunar eclipse events. I propose, for the time being*, a 27-day lunation period, which means that the Moon turns full, or new, again every 27 days, neatly moving full moons, or new moons, backwards 1 (one) day every month, which will culminate in a 9-year lunisolar cycle, consisting of 5 years with 12 lunar months ("moons") and 4 years of 13 moons. In total, 9 years are equal to 112 (lunar) months.
336 ÷ 27 = 12.444 = 112 ÷ 9
Maybe a holiday can be introduced in game for the dwarves to observe lunar festivals every new moon, full moon, or both, and even better, to celebrate a jubilee once 9 years is reached*. Jubilees can be seen as some small sort of achievement and will tie in smoothly a potential future holiday system to commemorate historical events, founding dates, and birthdays. Obviously this will have an effect on night- and were-creatures and this is, besides the jubilee system, my motivation for the thread.
*Hopefully once this is realized, a setting can be introduced later for lunation periods like 27.2, 27.5, or 27.9 days, each with different overarching lunisolar cycles.