Disks appear in photos taken December 21st

I got my 35mm Christmas photos back from the processor today. The strange disk anomalies that have heretofore only shown up on Halloween night shots have again shown up on photos taken on December 21st, the shortest day, the beginning of winter. The front stairs where such disks have appeared the most is again where they appeared this time. Two of these perfectly round, transparent, disks were at the head of my front stairs in one shot and the other shows one at the step level at the head of the stairs and the other was almost on the ceiling at the foot of the stairs. A thid picture taken of one of my dogs shows a small disk on the floor about a foot to the side of my dog. So far these disks have shown up on both digital and film type cameras and only on Halloween night and now the shortest day of the year. Interesting don't you think?