Apple script Intervalo de tiempo

Utilicé un gran script de CJK sin ningún problema, pero no estoy seguro de lo que pasa, recientemente me di cuenta de algunos resultados no válidos:

startDate = "2019-05-31" (Formato US) Luego se convierte a "31-05-2019".

MiFecha (ahora) = 01-06-2019

Resultado 31 días

    set creationDate to "2019-05-31"
    set [YearValCreation, MonthValCreation, dayValCreation] to the words of creationDate
    tell (current date) to set startDate to dayValCreation & "-" & MonthValCreation & "-" & YearValCreation --->>> "31-05-2019"

    set MyDate to short date string of (current date) --->>> "01/06/2019"
    set [dayVal, MonthVal, YearVal] to the words of MyDate
    tell (current date) to set MyDate to dayVal & "-" & MonthVal & "-" & YearVal ---->>>> "01-06-2019"
    set DateText to ""
    on timeInterval from startDate to endDate by units : 1
        tell (current date) to set [startDate, ¬
            day, [day, its month, year]] to ¬
            [it, 1, words of startDate]

        tell (current date) to set [endDate, ¬
            day, [day, its month, year]] to ¬
            [it, 1, words of endDate]

        (endDate - startDate) / units
    end timeInterval

    set dayResult to timeInterval from startDate to MyDate by days
    set dayResult to (round (dayResult * 1)) / 1 as integer
--->>> 31

Sólo liberar si la fecha es 30-05-2019 en lugar de 31-05-2019 tengo un resultado correcto