How to calculate first day of next Month

Suppose to start from a Tableau Desktop workbook with the data of Star Wars saga movies release date.

// Number of days current Month
DAY(
    DATEADD('day', -1,
        DATEADD('month', 1,
            DATETRUNC('month', [US Release Date])
        )
    )
)

You can download a working example of this Tableau Desktop workbook in the Resources area.