Get the days and hours between two datetimes in decimal format

Question

I have two dateTime fields, I need to get the amount of days and hours that have elapsed. This is the best i Can do but now im getting some errors.

Heres the error

System.TypeException: Invalid decimal: 0.-22

If the first date is 22/09/2016 12:30 and the second is 24/09/2016 14:00 I would want the results to be 2.1

public static Decimal getTimeDifference(Datetime now, Datetime endTime){
    if(now != null && endTime != null){
        Long dt1Long = endTime.getTime();
        Long dt2Long = now.getTime();
        Long milliseconds = dt2Long - dt1Long;
        Long seconds = milliseconds / 1000;
        Long minutes = seconds / 60;
        Long hours = minutes / 60;
        Long days1 = hours / 24;

        Long dt1Long2 = endTime.addDays((Integer)days1).getTime();
        Long dt2Long2 = now.getTime();
        Long milliseconds2 = dt2Long2 - dt1Long2;
        Long seconds2 = milliseconds2 / 1000;
        Long minutes2 = seconds2 / 60;
        Long hours2 = minutes2 / 60;
        Long days2 = hours2 / 24;
        return Decimal.valueOf(days1 + '.' + hours2);
    } else {
        return null;
    }
}

Answer 1

You can utilize Datetime's getTime() method and compare the two values.

Datetime firstTime = Datetime.newInstance(2016, 9, 22, 12, 30, 0);
Datetime secondTime = Datetime.newInstance(2016, 9, 23, 14, 00, 0);

Decimal millisecondsBetween = secondTime.getTime() - firstTime.getTime(); //NB: ths is important as to convert type
Decimal timeBetween = millisecondsBetween / 86400000;  //1000 * 60 * 60 * 24
System.debug(timeBetween);

Above is the sample code. I got the value 1.0625 which I think is correct. Please Note you need to convert the type into Decimal before divided by 86400000. Otherwise, the result would be 1.