The Aluvian Calendar

 For the year 998:

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During the Harvest, everyone in town must help. If a character isn't sick, dead, or aiding the harvest, he will be hanged on October 7th.

During Haven, the weather is too bad to go on adventures in the dungeon or overland, but characters can take care of indoor business.

During Holiday, exertion is strictly prohibited. Daily fines are 10 GP plus 100 GP per character level. 

During Open season, there are no restrictions on character actions.

On Sunday, no business will be done. Characters who are already out of town can keep moving (although they really shouldn't.) Clerics who exert themselves on Sunday will find they have no spells for eight days and nights. 

I rule that Anticlerics can work normally on Sunday. Instead, they are similarly restricted from sundown on Friday to sundown on Saturday. You could do that too, or that might be too complicated for your group.

During War, the characters must be available to the war effort in some capacity. No adventuring or other business takes place. Refusing this duty is desertion, which is, again, a hanging offense.