Doesn't seem like the pop-up inherits any classes from the input so I would say it's not possible.
Have you tried any other date picker widgets from the appstore as an alternative for that one page?
Did test it in a new test project and also this one has the same issue. Reason its close like the side off the screen is because:
You could add some custom styling using the CSS loader widget from the app store.. also turn to this post:
https://forum.mendix.com/link/questions/90103 for additional thoughts.
You can check out the set attribute widget. Maybe you can use it to apply custom styling to the date picker.