I have several holidays that fall toward the end of the year in the month equivalents of August through December.
Harvest tide (late August)--the crops are harvested and now work is suspended for one week of merriment, drinking and tavern tales. Bards frequently visit villagers to perform because that's the time when all the crops are sold and the village will have the most money. It's also when the tax collectors make their rounds (boo!).
Champion Games (last week of November and first week of December)--in the nation that I currently run, gladitorial games are every where in many nations. Many gladitors and prize fighters travel the nation and fight in local circuits and the it culminates to the Champion Games. The first week is exhibition matches which are the duel matches between noble houses, magic contests, chariot races, and such. The second week is the actual games where teams of gladiators fight the ultimate prize. During the two weeks, the city will swell to three times its size as people come from all around the nation to watch these games.
Symposium Decorum (the week after the Champions Games end--2nd week of December). This is the nobles' holiday where all the nobility, both great and small come together to air their complaints, settle disputes peacefully, or publicly shower the prince with tributes and gifts. No dueling or fighting is allowed during this week as it supposed to be time of forgiveness and comradery. All nobles are considered equal in the eyes of the Prince during this time. While the common folk don't participate in the Symposium Decorum, they love the gossip aspect of it and will take bets on the comings and goings of this or that house, who is to be knighted, and who has fallen into disfavor. Also, the gifts that the nobles bring are exotic, wild, and can be a circus in of itself so they proudly parade their gifts through the streets while on the way to the Royal Palace.
Star Festival (last three days of December) this is the time where Stars are considered their brightest in the night sky. A lot of businesses will be open in the late hours and taverns and alehouses are likely to be open throughout the whole night. It's also a holiday that promotes friendship and love and a committment to renew such bonds for the next year. It is also the holiday that is favored by the nobles to have masquerades in more alluring clothing (though in this nation, they are a bit conservative, so their dress styles are modest).
Right now, there's a civil war going in this nation which started during the Symposium Decorum (one House attempted to kill the dukes / duchesses of the other Houses in a quick bid for the throne).
That's a world of festivals all in its own.
