This is the iceberg problem. Component based programming has been around since probably the 60's. The easy part is making components. The hard part is making them (and this is the Holy Grail), portable. Pipes and Filters in the Unix OS is a simple example of one form of component development that actually works well.
It's not difficult to imagine a calendar component that needs to visually display vastly differently depending on how much space it's parent gives it. Currently there is no generic way to solve this.
Maybe I'm being naive here, but isn't this solved really by getting the width of a block level element rendered by the Calendar component?
Yeah it does mean you need to get the width and then render everything else, but it's doable.
Sure, it would be great to have a more component focused tool for FE development, but I think creating separate, fixed-width designs for tablet, phone, and desktop, with containers does the job fairly well. When the designs try to resize components for every use case you get more headache than it's worth.