Java Programming

Hi guys any help really appreciated as this is doing my head in (and I'm sure its something obvious)

Am trying to work out the difference in two times

public Time getFlightTime()
    {
        long diff = arTime.getTimeInMillis() - depTime.getTimeInMillis();
        
        Calendar temp = Calendar.getInstance();
        temp.setTimeInMillis(diff);
        return temp;
        
    }

have tried it with date and time creating the return object and it always ends up 59 mins out. Have had the function being called above print out "diff" and the time in milliseconds corresponds to the time it should be - ie 59 mins less than what it actually returns.

Any help - please?