In an ancient day and in an ancient land, the King wished to have a calendar. He wished for an accurate forecast of the weather each day, of knowing all holy days so they would not sneak up on him and make him unprepared. He wished for this year to be seamless, perfect, orderly. He commanded his masons and storm-watchers and court wizards and holy-men seers to the project.
In this land and at this time, writing on anything other then stone was considered peasant work. Wood and paper are weak, cheap materials found by rivers and forests; not dug from the Earth akin to gold and silver. The King's national calender could only be made of stone. And once it was complete, there was much rejoicing as it was unveiled on the first day of the year, showing the citizens the time for the harvests and the time for resting and the times for raining from the very first day of the year. By all accounts, the year was wonderfully foresaw and planned out; the witches made sure that it would be a peaceful and prosperous time. And on the second day of the year, the talk of the next year's calendar began around the King's court.
Of course, the King didn't like this. His calendar was written in stone, and so it shall be stone. And then he commanded his magicians to make every year after this one the exact same as the calendar.
Every day is the same as it was the last year. This doesn't apply to the people, animals, political situation, or anything like that. It does apply to the weather, but not to the climate. The land of the calendar was undone over centuries, not overnight. The circle of high priests who assassinated the first calendar-king prayed for the gods to free them, even as his birthday was celebrated yet again.
Eventually, the winds changed, the hills were beaten down by the hail and time. The fields were salted and buildings trampled by rival states. And yet, harvest festivals still occur. If the people be there or not, it doesn't matter. The power of the calender's law did not reach beyond the borders of the small old kingdom, but even so, the miles it held march to the first king's predictions.
March 24th is the King's birthday. Two of every animal native to the Kingdom must march to where his courtyard once stood and make their calls in tune with his birthday music even though the trumpeter is not there. This climate doesn't support this megafauna anymore; two giant, graying starved bears sit there pawing uselessly; their teeth long since fallen out and they have been too old and starved to support mating for a very long time. The moment a fitting animal passes into the territory, the old one dies with relief and the new one must take its place. Animals never native to the time of the calendar can make their way through the crowd of enchanted ones, freely biting and feeding on them as long as there is one more to spare.
April 2nd is the painter's day. Dirt and dust mixed with a pinch of water can be swirled with your fingers to produce any color you wish. Anything you paint with it remains vibrant until the next day, where it returns to the color of dust and dirt.
During the Equinox, somebody must open the twin doors to the holy temple. Through fate and chance, someone will wander or be driven to the doors, which are the only part of the building that remains standing with unfaded paint and cleanly-greased hinges, and must hold it open until the night comes. You can't walk away from that spot, but you can use your other hand to defend yourself, if needed.
During the Solstice, mirrors were once turned up to the sky during the hottest part of the day to blast birds down for sport and the feed the night's dinners; which was always roasted birds in the height of summer. The mirrors are gone; the shards and sand of the earth crawl back to their old places and shine weak lights upwards. Anyone flying or on stilts takes 1d4 damage per round during the day.
The Harvest is the longest festival of the year. The trees aren't around anymore, but sticks and stones are used to prop up any piece of wood in the rough shape and size of the old trees. They “grow” lumpy black fruit on the ends of their driftwood, falling down into baskets with holes in them. You can't leave the orchard until you eat at least one. There are no crops, but field mice and anyone stuck in the valley for this time pluck what little brown grass remains and pile it up, as though preparing for threshing.
The Rain comes and goes as it did before. The calendar shows the days of rains, the days of blooming flowers, the four seasons. But in the desert, there are only two seasons- the dry season, and the short wet season. The moisture for the rain the calendar forces must come from somewhere- the bodies in the desert have their blood boiled out, turned to mist to join the sparse clouds. The soil cannot absorb the moisture, becomes as dust, even though it is pelted with a pathetic mist everyday in facsimile of a storm. When the monsoons do come to this parched land, they are held back in great sheets by the power of the calendar, hovering a few yards above the ground, until it can hold it no longer and huge crashes of water slam into the ground like tidal waves.
December 3rd is the day of relieved patients. Anyone who is injured in the land of the calendars will slip into a relaxed state where they cannot do any kind of work or useful scouting; falling in and out of slumber. On the plus side, they heal double the normal rate for this day.
Finally, upon New Years Eve, the combustible material in the valley collects itself, forming tents of material over gsyers to propel itself into the sky for the fireworks that once filled the night air. Everything freezes at midnight, for half a minute or so, the clouds and people and animals. Nothing can move, but everyone can still think and feel. And when that minute is over, everything goes back to normal. It's January 1st now, the beginning of the calendar.
Anyone who finds the calendar near the heart of the land, and within the chamber of the old king, will find it a heavy stone wheel about 8 ft across. On its face are the days, drawn with symbols that meant words in simple pictographs that was common in the old days. The wheel is divided into months, weeks, days, and moments in time. Celebrations etched in its form have remained the same, and must remain the same, despite the old holidays not even being around anymore.
If the calendar is moved, time distortions follow it. It is also ungodly cumbersome, and requires many men and many hours to roll it. If you fail a save while rolling it there is a 50% chance it falls to the right or left and crushes someone to death. The calendar year remains in the land of the calendar, but will fade over the next century. The festival days will be celebrated less by the plants and animals, the few thirsty tribesman who still walk the old paths will find themselves leaving the land, one by one, to greener pastures. The monuments will finally start to crumble away. The power of the calendar will fade in its land, but the calendar is still a powerful artifact, containing essences of time and tradition within it.
Recovering the Calendar to civilization will invite certain collectors to pay for it. It is worth 180,000c and grants experience to the party members for that value the first day it experiences that is not written on its surface.