It was either May 21 2011 or 2012, and I remember that because in center city all that week a group of Christian people had been walking around with signs about the rapture. So on that day me and my roommates were sitting on our roof in the middle of the day and we looked up. In the distance (east and a little south from where we actually were) there appeared to be maybe 4 or 5 large white round things in the sky. At first we thought maybe they were balloons, but they didn't just float up. They went back and forth and up and down and would occasionally blip out and reappear somewhere else. Their movement and their apparent size (even though they were far away) made us question what they were. We didn't get any video, at the time I know I still had a flip phone. But after that I googled the date and found several videos of similar sightings from all around the world, which are now gone.