This is the day which promotes the protection and care of rabbits both domestic and wild around the world. International Rabbit Day will be held on September 26th this year. (It is an annual event and occurs on the 4th Saturday or Sunday of September.)
House Rabbit Society's chapters will be holding many events to promote International Rabbit Day. You can check out this list at their website to see what is scheduled at their chapters in the USA and elsewhere. Take the time out to attend one!