Today, April 24, is recognized as National Hairball Awareness Day. This "holiday" is "celebrated" annually on the last Friday in April. I think most cat owners are aware of hairballs without having to mark a special date on the calendar. The day is listed along with many other such awareness campaigns on the AVMA Veterinary Awareness Events page.
In our house, we are very lucky to have minimal problems with hairballs between our three boys.
With our previous long-haired tuxedo Arby, it was a regular battle that we fought with periodic doses of hairball preventative gels. Here's a photo of our sweet tuxedo boy enjoying a face-plant nap in a cat bed.