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));
}

假设这个月的日期不相关(即2011.1.1和2010.12.31之间的差为1)，date1 > date2为正值，date2 > date1为负值

((date1.Year - date2.Year) * 12) + date1.Month - date2.Month

或者，假设你想要两个日期之间的“平均月”的大致数字，下面的方法应该适用于所有日期，但日期差异非常大。

date1.Subtract(date2).Days / (365.25 / 12)

注意，如果您要使用后一种解决方案，那么您的单元测试应该声明应用程序设计使用的最宽日期范围，并相应地验证计算结果。

更新(感谢Gary)

如果使用“平均月份”方法，“每年平均天数”的更准确数字是365.2425。

扩展的Kirks结构与ToString(格式)和持续时间(长ms)

 public struct DateTimeSpan
{
    private readonly int years;
    private readonly int months;
    private readonly int days;
    private readonly int hours;
    private readonly int minutes;
    private readonly int seconds;
    private readonly int milliseconds;

    public DateTimeSpan(int years, int months, int days, int hours, int minutes, int seconds, int milliseconds)
    {
        this.years = years;
        this.months = months;
        this.days = days;
        this.hours = hours;
        this.minutes = minutes;
        this.seconds = seconds;
        this.milliseconds = milliseconds;
    }

    public int Years { get { return years; } }
    public int Months { get { return months; } }
    public int Days { get { return days; } }
    public int Hours { get { return hours; } }
    public int Minutes { get { return minutes; } }
    public int Seconds { get { return seconds; } }
    public int Milliseconds { get { return milliseconds; } }

    enum Phase { Years, Months, Days, Done }


    public string ToString(string format)
    {
        format = format.Replace("YYYY", Years.ToString());
        format = format.Replace("MM", Months.ToString());
        format = format.Replace("DD", Days.ToString());
        format = format.Replace("hh", Hours.ToString());
        format = format.Replace("mm", Minutes.ToString());
        format = format.Replace("ss", Seconds.ToString());
        format = format.Replace("ms", Milliseconds.ToString());
        return format;
    }


    public static DateTimeSpan Duration(long ms)
    {
        DateTime dt = new DateTime();
        return CompareDates(dt, dt.AddMilliseconds(ms));
    }


    public static DateTimeSpan CompareDates(DateTime date1, DateTime date2)
    {
        if (date2 < date1)
        {
            var sub = date1;
            date1 = date2;
            date2 = sub;
        }

        DateTime current = date1;
        int years = 0;
        int months = 0;
        int days = 0;

        Phase phase = Phase.Years;
        DateTimeSpan span = new DateTimeSpan();

        while (phase != Phase.Done)
        {
            switch (phase)
            {
                case Phase.Years:
                    if (current.AddYears(years + 1) > date2)
                    {
                        phase = Phase.Months;
                        current = current.AddYears(years);
                    }
                    else
                    {
                        years++;
                    }
                    break;
                case Phase.Months:
                    if (current.AddMonths(months + 1) > date2)
                    {
                        phase = Phase.Days;
                        current = current.AddMonths(months);
                    }
                    else
                    {
                        months++;
                    }
                    break;
                case Phase.Days:
                    if (current.AddDays(days + 1) > date2)
                    {
                        current = current.AddDays(days);
                        var timespan = date2 - current;
                        span = new DateTimeSpan(years, months, days, timespan.Hours, timespan.Minutes, timespan.Seconds, timespan.Milliseconds);
                        phase = Phase.Done;
                    }
                    else
                    {
                        days++;
                    }
                    break;
            }
        }

        return span;
    }
}

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {

        label3.Text = new DateDifference(Convert.ToDateTime("2018-09-13"), Convert.ToDateTime("2018-11-15")).ToString();
        label2.Text = new DateDifference(Convert.ToDateTime("2018-10-12"), Convert.ToDateTime("2018-11-15")).ToString();

        DateDifference oDateDifference = new DateDifference(Convert.ToDateTime("2018-11-12"));
       label1.Text  =   oDateDifference.ToString();

    }
}




public class DateDifference
{
    public DateTime start { get; set; }
    public DateTime currentDAte { get; set; }
    public DateTime origstart { get; set; }
    public DateTime origCurrentDAte { get; set; }

    int days { get; set; }
    int months { get; set; }
    int years { get; set; }

    public DateDifference(DateTime postedDate, DateTime currentDAte)
    {
        this.start = this.removeTime(postedDate);
        this.currentDAte = this.removeTime(currentDAte);
        this.origstart = postedDate;
        this.origCurrentDAte = currentDAte;

    }

    public DateDifference(DateTime postedDate)
    {
        DateTime currentDate_ = DateTime.Now;
        this.start = this.removeTime(postedDate);
        this.currentDAte = this.removeTime(currentDate_);
        this.origstart = postedDate;
        this.origCurrentDAte = currentDate_;
        if (start > this.currentDAte)
        {
            throw new Exception("Current date is greater than date posted");
        }
        this.compute();
    }

    void compute()
    {
        while (this.start.Year <= this.currentDAte.Year)
        {
            if (this.start.Year <= this.currentDAte.Year && (this.start.AddMonths(1) <= this.currentDAte))
            {
                ++this.months;
                this.start = this.start.AddMonths(1);
            }

            if ((this.start.Year == this.currentDAte.Year) && (this.start >= this.currentDAte.AddMonths(-1) && this.start <= this.currentDAte))
            {
                break;
            }
        }

        while (this.start.DayOfYear < this.currentDAte.DayOfYear)
        {
            ++this.days;
            this.start = start.AddDays(1);
        }

        if (this.months > 11)
        {
            while (this.months > 11)
            {
                ++this.years;
                this.months = months - 12;
            }
        }

    }


    public override string ToString()
    {
        if (this.start > this.currentDAte)
        {
            throw new Exception("Current date is greater than date posted");
        }
        String ret = this.ComposeTostring();
        this.reset();
        return ret;
    }

    private String ComposeTostring()
    {
        this.compute();
        if (this.years > 0)
        {
            if (this.months > 0)
            {
                if (this.days > 0)
                {
                    return String.Format("{0} year{1}, {2} month{3} && {4} Day{5} ago", this.years, plural(this.years), this.months, plural(this.months), this.days, plural(this.days));
                }
                return String.Format("{0} year{1}, {2} month{3} ago", this.years, plural(this.years), this.months, plural(this.months));
            }
            else
            {
                if (this.days > 0)
                {
                    return String.Format("{0} year{1},{2} day{3} ago", this.years, plural(this.years), this.days, plural(this.days));
                }

                return String.Format("{0} year{1} ago", this.years, plural(this.years));

            }
        }

        if (this.months > 0)
        {
            if (this.days > 0)
            {
                return String.Format("{0} month{1}, {2} day{3} ago", this.months, plural(this.months), this.days, plural(this.days));
            }
            else
            {
                return String.Format("{0} month{1} ago", this.months, plural(this.months));
            }
        }

        if ((this.origCurrentDAte - this.origstart).Days > 0)
        {
            int daysDiff = (this.origCurrentDAte - this.origstart).Days;
            this.origstart = this.origstart.AddDays(daysDiff);
            int HoursDiff = (this.origCurrentDAte - this.origstart).Hours;
            return String.Format("{0} day{1}, {2} hour{3} ago", daysDiff, plural(daysDiff), HoursDiff, plural(HoursDiff));

        }
        else if ((this.origCurrentDAte - this.origstart).Hours > 0)
        {
            int HoursDiff = (this.origCurrentDAte - this.origstart).Hours;
            this.origstart = this.origstart.AddHours(HoursDiff);
            int MinDiff = (this.origCurrentDAte - this.origstart).Minutes;
            return String.Format("{0} hour{1}, {2} minute{3} ago", HoursDiff, plural(HoursDiff), MinDiff, plural(MinDiff));
        }
        else if ((this.origCurrentDAte - this.origstart).Minutes > 0)
        {

            int MinDiff = (this.origCurrentDAte - this.origstart).Minutes;
            this.origstart = this.origstart.AddMinutes(MinDiff);
            int SecDiff = (this.origCurrentDAte - this.origstart).Seconds;
            return String.Format("{0} minute{1}, {2} second{3} ago", MinDiff, plural(MinDiff), SecDiff, plural(SecDiff));
        }
        else if ((this.origCurrentDAte - this.origstart).Seconds > 0)
        {
            int sec = (this.origCurrentDAte - this.origstart).Seconds;
            return String.Format("{0} second{1}", sec, plural(sec));
        }

        return "";
    }

    String plural(int val)
    {
        return (val > 1 ? "s" : String.Empty);
    }

    DateTime removeTime(DateTime dtime)
    {
        dtime = dtime.AddHours(-dtime.Hour);
        dtime = dtime.AddMinutes(-dtime.Minute);
        dtime = dtime.AddSeconds(-dtime.Second);
        return dtime;
    }

    public void reset()
    {

        this.days = 0;
        this.months = 0;
        this.years = 0;
        this.start = DateTime.MinValue;
        this.currentDAte = DateTime.MinValue;
        this.origstart = DateTime.MinValue;
        this.origCurrentDAte = DateTime.MinValue;
    }
}

我只是需要一些简单的东西来满足例如，只输入月份/年的就业日期，所以希望工作的年份和月份不同。这就是我所使用的，只是为了实用

public static YearsMonths YearMonthDiff(DateTime startDate, DateTime endDate) {
    int monthDiff = ((endDate.Year * 12) + endDate.Month) - ((startDate.Year * 12) + startDate.Month) + 1;
    int years = (int)Math.Floor((decimal) (monthDiff / 12));
    int months = monthDiff % 12;
    return new YearsMonths {
        TotalMonths = monthDiff,
            Years = years,
            Months = months
    };
}

net小提琴

简单的修复。工作的100%

        var exactmonth = (date1.Year - date2.Year) * 12 + date1.Month - 
        date2.Month +  (date1.Day >= date2.Day ? 0 : -1);
        Console.WriteLine(exactmonth);