Explanation of the Blue Moon

OK so David had a chance to read my blog and he once again explained the reason for the Blue Moon. He said that it only happens like every 10 years as to when you have a full moon in the same month twice. So the month of December we had two full moons. So when you have the second full moon like we did at that the end of December its called Blue Moon. How cool to learn something and I actually listened this time.