>>>He says: We still have only one month completed since August 5th and it gives 3
>>>
>>>So, how would a timespan fit in - given that the biggest unit a timespan knows about is a Day - no months, no years
>>>http://msdn.microsoft.com/en-us/library/system.timespan.aspx
>>>
>>>Also, a timespan doesn't have a starting point - ie a starting DateTime
>>
>>OK - we need a DateTimeSpan :-}

   public struct DateTimeSpan
>>    {
>>        public DateTimeSpan(int years, int months, int days, int hours, int minutes, int seconds)
>>        {
>>            Years = years; Months = months; Days = days;
>>            Hours = hours; Minutes = minutes; Seconds = seconds;
>>        }
>>
>>        public int Years;
>>        public int Months;
>>        public int Days;
>>        public int Hours;
>>        public int Minutes;
>>        public int Seconds;
>>
>>        public override string ToString()
>>        {
>>            return string.Format("Years:{0} Months:{1} Days:{2} Hours:{3} Minutes:{4} Seconds:{5}",
>>                Years, Months, Days, Hours, Minutes, Seconds);
>>        }
>>    }

I tried this:

static DateTimeSpan GetDateDiff(DateTime startDate, DateTime endDate)
>>        {
>>            int year = endDate.Year;
>>            int month = endDate.Month;
>>
>>            TimeSpan startSpan = new TimeSpan(startDate.Day, startDate.Hour, startDate.Minute, startDate.Second);
>>            TimeSpan endSpan = new TimeSpan(endDate.Day, endDate.Hour, endDate.Minute, endDate.Second);
>>
>>            if (endSpan - startSpan < new TimeSpan(0))
>>            {
>>                month -= 1;
>>                if (month == 0)
>>                {
>>                    month = 12;
>>                    year -= 1;
>>                }
>>            }
>>            TimeSpan ts = endDate.Subtract(new DateTime(year, month, startDate.Day, startDate.Hour, startDate.Minute, startDate.Second));
>>            return new DateTimeSpan(year - startDate.Year, month - startDate.Month, ts.Days, ts.Hours, ts.Minutes, ts.Seconds);
>>        }

Test:

DateTime earlierDate = new DateTime(2006, 1, 12,23, 15, 12);
>>DateTime laterDate = new DateTime(2010, 1, 4, 9, 55, 40);
>>
>>            for (int i = 0; i < 1000; i++)
>>            {
>>                DateTimeSpan dts = GetDateDiff(earlierDate, laterDate);
>>                Console.WriteLine("From:{0} To:{1}", earlierDate, laterDate);
>>                Console.WriteLine(dts);
>>
>>                if (earlierDate.AddYears(dts.Years).AddMonths(dts.Months).AddDays(dts.Days)
>>                    .AddHours(dts.Hours).AddMinutes(dts.Minutes).AddSeconds(dts.Seconds) != laterDate)
>>                    throw new Exception("Crap code");
>>
>>                laterDate = laterDate.Subtract(new TimeSpan(1, 20, 10));
>>            }

Maybe could be simplified more but at least GetDateDiff() is a bit shorter...
>
>
>Currently busy with fairly complex xbrl stuff ...
>
>Will have a look at it when time permits - hopefully during the weekend
>
>Hope to find a bug or at least something better ;)

Either would be distinctly possible :-}
Hmmm - what's xbrl ?