Today is Let It Go Day, a holiday where you're supposed to just let go of whatever emotional baggage, grudges, or other issues you've been hanging onto. It's the type of holiday that leads one to wonder who came up with such an idea, and why, and who actually celebrates such a thing. Odd holidays such as this, while trivial in the real world, make for interesting major holidays in fantasy or science fiction worlds.
Let It Go Day in your setting might be celebrated by a character's old enemy or rival showing up to bury the hatchet. This could be sincere, requiring the character to develop trust, or only appear to be sincere in an attempt to lure the character into a trap. It may be as simple as forcing the character to deal with an estranged friend or family member.
For games where characters have disadvantages, it might offer them a chance to resolve those issues. A character with an addiction may resolve to get help. A character who has lost his sanity or who has a phobia may confront the object of his fears and gain some sort of breakthrough. It may also be a time to accept any unwelcome changes that have happened within the setting recently.
In any case, Let It Go Day is the sort of holiday that can create adventure hooks in any sort of setting, and lead to interesting character development and roleplaying.
For more information on using obscure real-world holidays in roleplaying games, visit UncleBear.com