Bootstrap 4 alpha6 on Chrome 55 on Windows.
Renders properly in Firefox and Edge.
Please check your testcase. It doesn't contain an input group or a submit button as per the screenshot, which leads me to believe you've posted the wrong code. Per this StackOverflow question, support for <input type="datetime"> has been removed from most browsers, so the element renders the same as any other textbox (confirmed in Chrome 56). <input type="datetime-local">, however, is supported by Chrome and displays correctly.
Sorry, that test case somehow got wrong. To clarify I am referring to type date, not datetime or datetime-local.
Yep, okay. Confirmed on Chrome 56.
The issue also exists with datetime-local
please see this testcase: https://jsbin.com/kihosoviyu/1/edit?html,output
running chrome on windows.
Fix is to change .input-group .form-control to flex-direction: row;. It's currently column, which I think makes the elements inside the date text box layout vertically.
Actually, will be fixed when #21716 lands.