At this time of year, everyone is rushing about preparing or celebrating some sort of holiday. Special dishes are prepared and far-flung families reunite around the table. It's the perfect setting for any number of stories which is why so many writers use special occasions as the impetus for their plots.
I've used this device many, many times. I've had mysteries taking place around someone's birthday or anniversary. One of my plays takes place at a high school graduation, one at a pre-Oscar party.
Special occasions can bring together people of various backgrounds who all have one thing in common. Old rivalries can flare. Old loves can be revisited. New loves can blossom. Everyone is supposed to be on their best behaviour, but what happens when a few glasses of champagne have been ingested?
I like writing plots that give a firm reason for these people to know each other and a special occasion raises the emotional stakes. For example: A wedding. A time of joy but also a time of stress and huge expectations. For every ten people with tears in their eyes as they relive their own happy love stories there's someone who's reliving a bad relationship and feeling bitter. The ideas for plot lines are endless!
Gathering people for any event gives the writer the opportunity to have characters with long personal histories. Everyone knows everyone in their high school class. Strangers aren't going to be invited to a birthday party (although unexpected house guests can be fun). Imagine yourself as the new boyfriend or girlfriend at a family event. Are you instantly accepted or do you feel they eyes of judgment upon you? It would be an interesting POV.
One of the reasons I use special occasions so often is that everyone can identify with the situation. Not all of us have been to dinner with royalty, but we've all had birthdays. The reader has to get to know all the characters and their quirks fairly quickly. Why not give them a familiar situation?
Consider the wealth of writing opportunities offered by special occasions. It's a great gift for any writer.