I seem to have a problem of that sometimes I enter items into my calendar on my iPhone and then they later completely vanish. I also access calendar from my iPad and MacBook. The problem is possibly more frequent with appointments entered into the past. For example, sometimes I enter something after it has taken place just so in the future I can go back and see when the last time I did it was. Does anyone know what possible explanations for this might be? Is it conceivable my iPad is overwriting the calendar on my iPhone or something like that?