Seems like you and @Eric_Penn have this pretty much sorted already…
But yes, the original issue you’re seeing Dan is because date picker is giving a datetime that’s your date at midnight… and in your first screen shot, June 3rd at 12:00am is the end of June 2nd.
By writing your date+1 math column to the displayed end date, you’re getting the view you originally expected… but then you do have to be sure you’re not reporting an extra day to payroll.
I would suggest using the math column to write your date plus 23hr & 59 min (or just 0.9999 day), rather than + 1 day. This will have your calendar appear the same, but when you view the end date as a date only column, it still shows the real end date… it’s just that by adding 23:59 to it, you’re visually seeing all of that day. Minor difference, but it could reduce potential confusions later with payroll.