计算两个日期之间的小数月数(C#)

我希望两天之间的日历月数(可能是小数(，例如2013年1月2日至2014年2月15日应在12.5个月左右。

我很惊讶没有在谷歌上找到答案。

编辑：我最终写了一些代码——如果有人需要同样的代码，下面是我的答案(我今天的好因果报应：(

/// <summary>
/// Number of total calendar months between two dates. If day of month is different,
/// gives fractional approximation using average days per month.
/// </summary>
public static double MonthsBetween(DateTime start, DateTime finish)
{
    //handle if dates switched - calculation same but there's a negative result:
    double multiplier;
    if(finish < start)
    {
        var temp = start;
        start = finish;
        finish = temp;
        multiplier = -1;
    }
    else
    {
        multiplier = 1;
    }
    //1) 20 Mar 2012 - 13 Jan 2014 --> 2*12 months
    //2) 15 Jan 2011 - 30 Jul 2012 --> 1*12 months
    //3) 20 Jan 2010 - 25 Jan 2010 --> 0*12 months
    double totalMonths = (finish.Year - start.Year)*12;
    //1) 20 Mar 2012 - 13 Jan 2014 --> 2*12 + 1 - 3 = 22 months
    //2) 15 Jan 2011 - 30 Jul 2012 --> 1*12 + 7 - 1 = 18 months
    //3) 20 Jan 2010 - 25 Jan 2010 --> 0*12 + 0 months = 0 months
    totalMonths += finish.Month - start.Month;
    ///Now we have "1st of the month to 1st of the month" difference. Days can only be approximated,
    ///since each month has a different number of days. Statistically (http://en.wikipedia.org/wiki/Month#Julian_and_Gregorian_calendars):
    const double averageDaysInMonth = 30.436875;
    ///Remove the days we've included in the starting month (not in actual period):
    totalMonths -= start.Day / averageDaysInMonth;
    ///Add the days in the finish month (weren't yet included, since had "1st to 1st"):
    totalMonths += finish.Day / averageDaysInMonth;
    //1) 20 Mar 2012 - 13 Jan 2014 --> 2*12 + 1 - 3 - 20/30 + 13/30 = 22 - 7/30 = 21.76 months
    //2) 15 Jan 2011 - 30 Jul 2012 --> 1*12 + 7 - 1 - 15/30 + 30/30 = 18 + 15/30 = 18.5 months
    //3) 20 Jan 2010 - 25 Jan 2010 --> 0*12 + 0 - 20/30 + 25/30 = 0 + 5/30 = 0.17 months
    return totalMonths * multiplier;
}

同样，我意识到，几年来我也需要类似的东西。这也是代码，以防它对某人有所帮助：

/// <summary>
/// Number of total calendar years between two dates. Gives fractional 
/// approximation if months/days differ.
/// </summary>
public static double YearsBetween(DateTime start, DateTime finish)
{
    //handle if dates switched - calculation same but there's a negative result:
    double multiplier;
    if (finish < start)
    {
        var temp = start;
        start = finish;
        finish = temp;
        multiplier = -1;
    }
    else
    {
        multiplier = 1;
    }
    //1) 20 Mar 2012 - 13 Jan 2014 --> 2 years
    //2) 15 Jan 2011 - 30 Jul 2012 --> 1 year
    //3) 20 Jan 2010 - 25 Jan 2010 --> 0 years
    double totalYears = finish.Year - start.Year;
    ///Now we have "1st of the year to 1st of the year" difference. Days/months can only be approximated,
    ///since each year has a different number of days. Statistically (http://en.wikipedia.org/wiki/Year):
    const double averageDaysPerYear = 365.2425;
    ///Remove the days we've included in the starting year (not in actual period):
    totalYears -= start.DayOfYear / averageDaysPerYear;
    ///Add the days in the finish year (weren't yet included, since had "Jan 1 to Jan 1"):
    totalYears += finish.DayOfYear / averageDaysPerYear;
    //1) 20 Mar 2012 - 13 Jan 2014 --> 2 - ~(2*30+20)/365 + 13/365 = 1.82 years
    //2) 15 Jan 2011 - 30 Jul 2012 --> 1 - 15/365 + ~(6*30+30)/365 = 1.53 years
    //3) 20 Jan 2010 - 25 Jan 2010 --> 0 - 20/365 + 25/365 = 0.01 years
    return totalYears * multiplier;
}

TimeSpan timeSpan = laterDate.Subtract(earlierDate);
var monthsCount = timeSpan.TotalDays / MonthDaysCount;

var startTime = Convert.ToDateTime("02/01/2013");
var endTime = Convert.ToDateTime("15/02/2014");
var span = endTime.Subtract(startTime);
Console.WriteLine("Time Difference (months): " + Math.Round((decimal)span.Days/30,1));

DateTime date1 = new DateTime(2013, 1, 2);
DateTime date2 = new DateTime(2014, 2, 15);
TimeSpan difference = date2.Subtract(date1);
double elapsedMonths = difference.TotalDays / 30;

(new DateTime(2013, 1, 2) - new DateTime(2014, 2, 15)).TotalDays / (365.25 / 12)