Up to OJB's Photos List Blue Moon A "blue moon" happens when a full moon occurs at the end of the month, meaning there was a previous one near the beginning of that same month (the moon takes 29.5 days each orbit but most months are 30 or 31 days). As you can see from this photo, it has nothing to do with the colour of the moon (it isn't blue) and really isn't any different from any other full moon. | 
PHOTO PAGE