It's actually looks very familiar from current app, but I had reiterating the view mapping from ground up, to be able to mapping well with all iOS devices, from 3.5" screen, to 4", 4.7", 5.5" to 7.9", 9.7" and iPad Pro 13".
I am not cater for each screen perfectly per inch but rather to use screen's aspect ratio.
Refer to figure above, that is the rough sketch of the clock and calendar mapping according to screensize. Each screen can be divided into blocks. The number of block is based on aspect ratio. As you can know on iPhone, 4", 4.7", and 5.5" screen has the same aspect ratio which means the mapping can be satisfied with one same rule. So what is the rule. Basically to tell the clock which position it should located in coordinate form. For example for vertical iPhone 6, it's 4x7 blocks, for clock is (x:1,y:1,width:2,height:2), and calendar is (x:0,y:3,width:4,3). The coordinate and grid size will automatically adjusted according to actual screen size.
By doing this I can fit the widget in all condition that has been presetted. But what if Apple announce new device that don't being currently supported aspect ratio. Honestly I don't know. Surely breaks the view mapping.
But so far what I see is the aspect ratio is very consistent and already matured, you may see the next gen iPhone will have the same aspect ratio as now. As well goes to iPad. So don't worry too much.
This FC Calendar is on going process, it's on testing, and it's bit nervous to release because it is a new project from ground up, but we need to make it backward compatible from previous update. Meaning, we have to preserve user's NSUserDeafults, so that new app will have the same behaviour like the current app has in term of settings.
This utilities aka widget app with this grid system will be evolve into more widgets in the future. I love how it being engineered to be more flexible than rather using fixed width and heigth as what I did, and have simple condition between iPhone 3.5" and 4", and now there are so many devices to support natively on iOS. But for other cases we can just use Autolayout feature, which can solve multi-screen type problems.
So wait the update on the App Store soon.