This is managed thru the option 'minOption' of fullCalendar which is not available as a property yet. If you know how to adapt the widget you can add it.
of course creating a property and adapting the interface is the most elegant way.
There was a pull request for the Calendar widget that addresses this feature (scrollTime). I have included this: https://github.com/mendix/Calendar/commit/225167cb6dcd63ee21d59cf39c284620daf5960f
We will include this in the next release later today (waiting for some feedback on an unrelated issue first).
If there are more feature requests, please include a pull request on Github or create an issue there