基于上面出色的DateTimeSpan工作，我将代码规范化了一些;这似乎很有效:

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;
  }
}

最精确的方法是以月为单位的分数返回差值:

private double ReturnDiffereceBetweenTwoDatesInMonths(DateTime startDateTime, DateTime endDateTime)
{
    double result = 0;
    double days = 0;
    DateTime currentDateTime = startDateTime;
    while (endDateTime > currentDateTime.AddMonths(1))
    {
        result ++;

        currentDateTime = currentDateTime.AddMonths(1);
    }

    if (endDateTime > currentDateTime)
    {
        days = endDateTime.Subtract(currentDateTime).TotalDays;

    }
    return result + days/endDateTime.GetMonthDays;
}

我当时在做一个项目，只需要几年和几个月。

/// <summary>
/// Get the total months between two date.  This will count whole months and not care about the day.
/// </summary>
/// <param name="firstDate">First date.</param>
/// <param name="lastDate">Last date.</param>
/// <returns>Number of month apart.</returns>
private static int GetTotalMonths(DateOnly firstDate, DateOnly lastDate)
{
    int yearsApart = lastDate.Year - firstDate.Year;
    int monthsApart = lastDate.Month - firstDate.Month;
    return (yearsApart * 12) + monthsApart;
}

private static int GetTotalMonths(DateTime firstDate, DateTime lastDate)
{
    return GetTotalMonths(DateOnly.FromDateTime(firstDate), DateOnly.FromDateTime(lastDate));
}

这里有一个简单的解决方案，至少对我来说是有效的。它可能不是最快的，因为它在循环中使用了很酷的DateTime的AddMonth功能:

public static int GetMonthsDiff(DateTime start, DateTime end)
{
    if (start > end)
        return GetMonthsDiff(end, start);

    int months = 0;
    do
    {
        start = start.AddMonths(1);
        if (start > end)
            return months;

        months++;
    }
    while (true);
}

这是我所需要的。对我来说，一个月的哪一天并不重要，因为它总是碰巧是一个月的最后一天。

public static int MonthDiff(DateTime d1, DateTime d2){
    int retVal = 0;

    if (d1.Month<d2.Month)
    {
        retVal = (d1.Month + 12) - d2.Month;
        retVal += ((d1.Year - 1) - d2.Year)*12;
    }
    else
    {
        retVal = d1.Month - d2.Month;
        retVal += (d1.Year - d2.Year)*12;
    }
    //// Calculate the number of years represented and multiply by 12
    //// Substract the month number from the total
    //// Substract the difference of the second month and 12 from the total
    //retVal = (d1.Year - d2.Year) * 12;
    //retVal = retVal - d1.Month;
    //retVal = retVal - (12 - d2.Month);

    return retVal;
}

你可以这样做

if ( date1.AddMonths(x) > date2 )