DateTimeInputWidget is currently set to display: inline-block at the same time got width: 100% applied.
Unlimiting inputs makes sense when user can enter more content into the field as inputs should communicate the lenght of content wishful and needed. In this case it simply makes no sense to have the input take up the full width of the form.
We should remove this rule and consider probably to add a min-width: 24.275em rule to the handle to be aligned with the width of the calendar dropdown.
Proposal (one in long-form, one in short):
With calendar dropdown: