Happy Hogmanay! Or if you're in central Australia or points east, Happy New Year!
This is my 200th post here, apparently. There's a noteworthy number for you.
A year ends, a year begins. It's an arbitrary placement nine days after the more logical choice of the winter solstice, but it's the one I'm stuck with in this culture. Time to look back and reflect, time to look forward and hope.
Fantastical settings sometimes put a lot of weight on the significance of years, dates and numbers and in some it might be more than symbolic. Prophecies tied to specific times or lunar cycles might be accurate, astrology might have a defining power, and that calendar counting down to Doomsday might just be right.
A more SF-ish version might have the significance people assign to dates be a factor. So the world ends at midnight because that's when the new atomic clock goes online, to borrow an example from of all things Doctor Who: The Movie.
And the PCs might not know about every significant date. Without looking, can you tell me when St. Swithin's Day is? That might lead to forty days of rain. And in a setting with a higher Weird Level than our own, this might be literally true.
Or how about the nights that vampires in Buffy are supposed to feast or fast?
And then there's the wider symbolic weight of endings and beginnings, births and deaths, the cycle of seasons, the rituals of entering a new house or christening a new ship with champagne.
As someone who's likely to be first footing at least one house tomorrow morning, I know some traditions have more importance than others, some are just a bit of fun. Does your setting have traditions like that, which don't "matter" in objective terms? They can add a lot to bring a game world alive.