Answer by Dan Sutton for Difference in months between two dates

Based on the excellent DateTimeSpan work done above, I've normalized the code a bit; this seems to work pretty well:

public class DateTimeSpan{  private DateTimeSpan() { }  private DateTimeSpan(int years, int months, int days, int hours, int minutes, int seconds, int milliseconds)  {    Years = years;    Months = months;    Days = days;    Hours = hours;    Minutes = minutes;    Seconds = seconds;    Milliseconds = milliseconds;  }  public int Years { get; private set; } = 0;  public int Months { get; private set; } = 0;  public int Days { get; private set; } = 0;  public int Hours { get; private set; } = 0;  public int Minutes { get; private set; } = 0;  public int Seconds { get; private set; } = 0;  public int Milliseconds { get; private set; } = 0;  public static DateTimeSpan CompareDates(DateTime StartDate, DateTime EndDate)  {    if (StartDate.Equals(EndDate)) return new DateTimeSpan();    DateTimeSpan R = new DateTimeSpan();    bool Later;    if (Later = StartDate > EndDate)    {      DateTime D = StartDate;      StartDate = EndDate;      EndDate = D;    }    // Calculate Date Stuff    for (DateTime D = StartDate.AddYears(1); D < EndDate; D = D.AddYears(1), R.Years++) ;    if (R.Years > 0) StartDate = StartDate.AddYears(R.Years);    for (DateTime D = StartDate.AddMonths(1); D < EndDate; D = D.AddMonths(1), R.Months++) ;    if (R.Months > 0) StartDate = StartDate.AddMonths(R.Months);    for (DateTime D = StartDate.AddDays(1); D < EndDate; D = D.AddDays(1), R.Days++) ;    if (R.Days > 0) StartDate = StartDate.AddDays(R.Days);    // Calculate Time Stuff    TimeSpan T1 = EndDate - StartDate;    R.Hours = T1.Hours;    R.Minutes = T1.Minutes;    R.Seconds = T1.Seconds;    R.Milliseconds = T1.Milliseconds;    // Return answer. Negate values if the Start Date was later than the End Date    if (Later)      return new DateTimeSpan(-R.Years, -R.Months, -R.Days, -R.Hours, -R.Minutes, -R.Seconds, -R.Milliseconds);    return R;  }}