Go through old magazines and/or newspapers from the past year, or to your local library (this is fun research) to search through old news articles. Find 20 events that took place in the past year. Make a list of these events, and have your guests guess which month the event took place in. For example- "During what month did Star Wars II open in theatres?" Whoever guesses the most right wins a prize.
You can either read the list while players mark their answers or you can print up a sheet with all the events and have individuals or couples fill them out during the party. Then read off the answers.