public static Integer calculateDateDifferenceHours(Datetime date1, Datetime date2) {
Long dtStartLong = date1.getTime();
Long dtEndLong = date2.getTime();
Long milliseconds = (dtEndLong - dtStartLong);
Long seconds = milliseconds / 1000;
Long minutes = seconds / 60;
Long hours = minutes / 60;
Long days = hours / 24;
return Integer.valueOf(hours);
}