I've got the same calendar problem on my iphone 4s. When I updated the phone to ios7, besides the fact that I hate the look of the new calendar, all my appointments went away. The appointments are OK on my iPad after its ios7 update and the appointments are also on my macbook pro (in My Yahoo), but not on the iphone 4s. Is this going to be corrected in an ios7 update in the near future or should I take the steps of going back to ios6, where I was perfectly happy?
CT Santa Cruz