Up & Down Buttonhole/Blanket Stitch or Mirrored Buttonhole/Blanket Stitch. Whatever you call it, it's fun to do and fairly easy. Check the links at Tuesday Stitchers for tutorials and examples and check out how others have used it in their various projects.
I was a bit slow to 'get' this stitch til I found the tutorial that showed it upside down from the others. You can see where I stopped and started in the closeup below as the stitches are a bit off. Another learning point in working with circles!
The historic event for July 10 is the year 1921 and birthday of the inventor of the smiley face...no it really was not Forrest Gump. It was Harvey Ball, an american inventor and commercial artist who worked for the State Mutual Life Assurance Company in Massachusetts in 1963. He was paid $45 for the 10 minutes it took to create an image to raise the morale of the employees. He never received any other income from the design and was pleased it made other people happy.