What is the best way to synchronize contacts and events between Thunderbird on a Windows PC and Contacts and Calendar on an iPhone 4 with iOS 7 and an iPad Air with iOS 8? A friend of mine is in this situation, and I could not help her right away. She has been using BirdieSync (on PC and iPhone/iPad) but although BirdieSync says it would be synchronizing it actually seems not to do it. Can this be done via iCloud? And if, how?