/// <summary>
/// Gets the scalar difference between two dates given a <see cref="DateInterval"/> value.
/// </summary>
/// <param name="interval">The interval to calculate</param>
/// <param name="start">The start date</param>
/// <param name="end">The end date</param>
/// <param name="excludeEndDate">If true, the difference is exclusive of the end date</param>
/// <returns></returns>
public static int GetDifference(DateInterval interval, DateTime start, DateTime end, bool excludeEndDate = false)
{
var sum = 0;
var span = new DateSpan(start, end);
switch (interval)
{
case DateInterval.Years:
sum += span.Years;
break;
case DateInterval.Months:
if (span.Years > 0)
{
sum += span.Years * 12;
}
sum += span.Months;
sum += span.Weeks / 4; // Helps resolve lower resolution
break;
case DateInterval.Weeks:
sum = GetDifferenceInDays(start, span, excludeEndDate) / 7;
break;
case DateInterval.Days:
sum = GetDifferenceInDays(start, span, excludeEndDate);
break;
case DateInterval.Hours:
sum = GetDifferenceInDays(start, span, excludeEndDate) * 24;
sum += span.Hours;
break;
case DateInterval.Minutes:
sum = GetDifferenceInDays(start, span, excludeEndDate) * 24 * 60;
sum += span.Hours * 60;
sum += span.Minutes;
break;
case DateInterval.Seconds:
sum = GetDifferenceInDays(start, span, excludeEndDate) * 24 * 60 * 60;
sum += span.Hours * 60 * 60;
sum += span.Minutes * 60;
sum += span.Seconds;
break;
default:
throw new ArgumentOutOfRangeException("interval");
}
return sum;
}
private static int GetDifferenceInDays(DateTime start, DateSpan span, bool excludeEndDate = true)
{
var sum = 0;
if (span.Years > 0)
{
for (var i = 0; i < span.Years; i++)
{
var year = start.Year + i;
sum += DateTime.IsLeapYear(year) ? 366 : 365;
}
}
if (span.Months > 0)
{
for (var i = 1; i <= span.Months; i++)
{
var month = start.Month + i;
if (month >= 13)
{
month -= 12;
}
sum += DateTime.DaysInMonth(start.Year + span.Years, month);
}
}
sum += span.Weeks*7;
sum += span.Days;
if(excludeEndDate)
{
sum--;
}
return sum;
}