I assume you know the dates, so you can use the Global method yearDiff to
figure out the number of years between the two days.
You also ask about the number of days, but you start by stating you know the
number of date!? Anyway by extracting the dates from each other you get the
number of dates between the two dates: date1 - date2 = numOfDays.
I don't know about the number of months. Maybe you can find something in
.NET to calculate this.