It seems that the date picker widget in it's current form always occupies a set minimum width. Therefore, it can overflow the admin page body in some cases, as shown in the image blow:

(image taken from the the blog page template from the example project)

I was only able to "fix" this by decreasing the font size of the date picker, which is not an ideal fix.

This is for screen widths between 1024px and 1365px.