TimeSpan中获得这个信息，因为“月”是一个可变的计量单位。你需要自己计算，而且必须确定你想要的具体工作方式。2009年7月5日和2009年8月4日这样的日期应该产生一个月还是零个月的差异？如果你认为应该产生一个月，那么2009年7月31日和2009年8月1日呢？那是一个月吗？它是否只是日期的Month值之差，或者与实际时间段更相关？确定所有这些规则的逻辑都是非平凡的，所以你必须确定自己的规则并实现适当的算法。public static int MonthDifference(this DateTime lValue, DateTime rValue)
{
return (lValue.Month - rValue.Month) + 12 * (lValue.Year - rValue.Year);
}
rValue大于lValue，则返回值将为负数。如果您需要绝对差异值，可以使用以下代码：public static int MonthDifference(this DateTime lValue, DateTime rValue)
{
return Math.Abs((lValue.Month - rValue.Month) + 12 * (lValue.Year - rValue.Year));
}
我知道这是一个老问题，但是...
在.NET中纯粹地进行这项工作相对来说是很痛苦的。我建议使用我自己的Noda Time库，该库特别设计用于处理此类任务：
LocalDate start = new LocalDate(2009, 10, 6);
LocalDate end = new LocalDate(2009, 12, 25);
Period period = Period.Between(start, end);
int months = period.Months;
还有其他选项，例如，如果您只想计算跨年份的月份数量，您可以使用Period period = Period.Between(start, end, PeriodUnits.Months);
Period.Between。已经编辑了代码，所以它可以与NodaTime 1.3.1一起使用。 - Jon Skeet也许你不想了解月份分数；那这段代码呢？
public static class DateTimeExtensions // 日期时间拓展类
{
public static int TotalMonths(this DateTime start, DateTime end) // 计算两个日期之间相差的月份数
{
return (start.Year * 12 + start.Month) - (end.Year * 12 + end.Month); // 返回相差月份数
}
}
// Console.WriteLine(
// DateTime.Now.TotalMonths(
// DateTime.Now.AddMonths(-1))); // 输出 "1"
DateTime 和 DateTimeOffset 上非常简单的扩展方法来做这件事。我希望它能够像TimeSpan 的 TotalMonths 属性一样工作：即返回两个日期之间完整月份的计数，忽略任何不足一个月的部分。因为它基于 DateTime.AddMonths() ，所以它尊重不同的月份长度，并返回人们理解的月份期间。public static int GetTotalMonthsFrom(this DateTime dt1, DateTime dt2)
{
DateTime earlyDate = (dt1 > dt2) ? dt2.Date : dt1.Date;
DateTime lateDate = (dt1 > dt2) ? dt1.Date : dt2.Date;
// Start with 1 month's difference and keep incrementing
// until we overshoot the late date
int monthsDiff = 1;
while (earlyDate.AddMonths(monthsDiff) <= lateDate)
{
monthsDiff++;
}
return monthsDiff - 1;
}
而且它通过了所有这些单元测试用例:
// Simple comparison
Assert.AreEqual(1, new DateTime(2014, 1, 1).GetTotalMonthsFrom(new DateTime(2014, 2, 1)));
// Just under 1 month's diff
Assert.AreEqual(0, new DateTime(2014, 1, 1).GetTotalMonthsFrom(new DateTime(2014, 1, 31)));
// Just over 1 month's diff
Assert.AreEqual(1, new DateTime(2014, 1, 1).GetTotalMonthsFrom(new DateTime(2014, 2, 2)));
// 31 Jan to 28 Feb
Assert.AreEqual(1, new DateTime(2014, 1, 31).GetTotalMonthsFrom(new DateTime(2014, 2, 28)));
// Leap year 29 Feb to 29 Mar
Assert.AreEqual(1, new DateTime(2012, 2, 29).GetTotalMonthsFrom(new DateTime(2012, 3, 29)));
// Whole year minus a day
Assert.AreEqual(11, new DateTime(2012, 1, 1).GetTotalMonthsFrom(new DateTime(2012, 12, 31)));
// Whole year
Assert.AreEqual(12, new DateTime(2012, 1, 1).GetTotalMonthsFrom(new DateTime(2013, 1, 1)));
// 29 Feb (leap) to 28 Feb (non-leap)
Assert.AreEqual(12, new DateTime(2012, 2, 29).GetTotalMonthsFrom(new DateTime(2013, 2, 28)));
// 100 years
Assert.AreEqual(1200, new DateTime(2000, 1, 1).GetTotalMonthsFrom(new DateTime(2100, 1, 1)));
// Same date
Assert.AreEqual(0, new DateTime(2014, 8, 5).GetTotalMonthsFrom(new DateTime(2014, 8, 5)));
// Past date
Assert.AreEqual(6, new DateTime(2012, 1, 1).GetTotalMonthsFrom(new DateTime(2011, 6, 10)));
您需要自己处理日期时间。如何处理最后的存根日期将取决于您想要使用它的方式。
一种方法是计算月份，然后在末尾进行天数修正。例如：
DateTime start = new DateTime(2003, 12, 25);
DateTime end = new DateTime(2009, 10, 6);
int compMonth = (end.Month + end.Year * 12) - (start.Month + start.Year * 12);
double daysInEndMonth = (end - end.AddMonths(1)).Days;
double months = compMonth + (start.Day - end.Day) / daysInEndMonth;
private static int TotalMonthDifference(DateTime dtThis, DateTime dtOther)
{
int intReturn = 0;
bool sameMonth = false;
if (dtOther.Date < dtThis.Date) //used for an error catch in program, returns -1
intReturn--;
int dayOfMonth = dtThis.Day; //captures the month of day for when it adds a month and doesn't have that many days
int daysinMonth = 0; //used to caputre how many days are in the month
while (dtOther.Date > dtThis.Date) //while Other date is still under the other
{
dtThis = dtThis.AddMonths(1); //as we loop, we just keep adding a month for testing
daysinMonth = DateTime.DaysInMonth(dtThis.Year, dtThis.Month); //grabs the days in the current tested month
if (dtThis.Day != dayOfMonth) //Example 30 Jan 2013 will go to 28 Feb when a month is added, so when it goes to march it will be 28th and not 30th
{
if (daysinMonth < dayOfMonth) // uses day in month max if can't set back to day of month
dtThis.AddDays(daysinMonth - dtThis.Day);
else
dtThis.AddDays(dayOfMonth - dtThis.Day);
}
if (((dtOther.Year == dtThis.Year) && (dtOther.Month == dtThis.Month))) //If the loop puts it in the same month and year
{
if (dtOther.Day >= dayOfMonth) //check to see if it is the same day or later to add one to month
intReturn++;
sameMonth = true; //sets this to cancel out of the normal counting of month
}
if ((!sameMonth)&&(dtOther.Date > dtThis.Date))//so as long as it didn't reach the same month (or if i started in the same month, one month ahead, add a month)
intReturn++;
}
return intReturn; //return month
}
如果你需要计算不完整的月份，那么接受的答案就不能完全胜任。
以下是我为计算不完整月份所想出的解决方案：
/// <summary>
/// Calculate the difference in months.
/// This will round up to count partial months.
/// </summary>
/// <param name="lValue"></param>
/// <param name="rValue"></param>
/// <returns></returns>
public static int MonthDifference(DateTime lValue, DateTime rValue)
{
var yearDifferenceInMonths = (lValue.Year - rValue.Year) * 12;
var monthDifference = lValue.Month - rValue.Month;
return yearDifferenceInMonths + monthDifference +
(lValue.Day > rValue.Day
? 1 : 0); // If end day is greater than start day, add 1 to round up the partial month
}
我也需要计算一年内的部分年份差异。以下是我想出的解决方案：
/// <summary>
/// Calculate the differences in years.
/// This will round up to catch partial months.
/// </summary>
/// <param name="lValue"></param>
/// <param name="rValue"></param>
/// <returns></returns>
public static int YearDifference(DateTime lValue, DateTime rValue)
{
return lValue.Year - rValue.Year +
(lValue.Month > rValue.Month // Partial month, same year
? 1
: ((lValue.Month = rValue.Month)
&& (lValue.Day > rValue.Day)) // Partial month, same year and month
? 1 : 0);
}
YearDifference 函数存在逻辑错误，当 lValue.Month < rValue.Month 时 - 我已经修复了这个问题，你可能需要重新审查一下... - Stoborstatic int TotelMonthDifference(this DateTime dtThis, DateTime dtOther)
{
int intReturn = 0;
dtThis = dtThis.Date.AddDays(-(dtThis.Day-1));
dtOther = dtOther.Date.AddDays(-(dtOther.Day-1));
while (dtOther.Date > dtThis.Date)
{
intReturn++;
dtThis = dtThis.AddMonths(1);
}
return intReturn;
}
return (dtOther.Month - dtThis.Month) + 12 * (dtOther.Year - dtThis.Year);。 - Adam Robinson虽然这是一个老问题，但可能会对某些人有帮助。我使用了上面@Adam的答案，但是我检查了一下差异是否为1或-1，然后再检查是否为完整的日历月份差异。因此，21/07/55和20/08/55不是一个完整的月份，但是21/07/55和21/07/55则是。
/// <summary>
/// Amended date of birth cannot be greater than or equal to one month either side of original date of birth.
/// </summary>
/// <param name="dateOfBirth">Date of birth user could have amended.</param>
/// <param name="originalDateOfBirth">Original date of birth to compare against.</param>
/// <returns></returns>
public JsonResult ValidateDateOfBirth(string dateOfBirth, string originalDateOfBirth)
{
DateTime dob, originalDob;
bool isValid = false;
if (DateTime.TryParse(dateOfBirth, out dob) && DateTime.TryParse(originalDateOfBirth, out originalDob))
{
int diff = ((dob.Month - originalDob.Month) + 12 * (dob.Year - originalDob.Year));
switch (diff)
{
case 0:
// We're on the same month, so ok.
isValid = true;
break;
case -1:
// The month is the previous month, so check if the date makes it a calendar month out.
isValid = (dob.Day > originalDob.Day);
break;
case 1:
// The month is the next month, so check if the date makes it a calendar month out.
isValid = (dob.Day < originalDob.Day);
break;
default:
// Either zero or greater than 1 month difference, so not ok.
isValid = false;
break;
}
if (!isValid)
return Json("Date of Birth cannot be greater than one month either side of the date we hold.", JsonRequestBehavior.AllowGet);
}
else
{
return Json("Date of Birth is invalid.", JsonRequestBehavior.AllowGet);
}
return Json(true, JsonRequestBehavior.AllowGet);
}