我想添加希伯来文日历计算（或其他系统。全球化日历可以以相同的方式使用），使用此线程中的重写函数：

Public Shared Function CalculateAge(BirthDate As DateTime) As Integer
    Dim HebCal As New System.Globalization.HebrewCalendar ()
    Dim now = DateTime.Now()
    Dim iAge = HebCal.GetYear(now) - HebCal.GetYear(BirthDate)
    Dim iNowMonth = HebCal.GetMonth(now), iBirthMonth = HebCal.GetMonth(BirthDate)
    If iNowMonth < iBirthMonth Or (iNowMonth = iBirthMonth AndAlso HebCal.GetDayOfMonth(now) < HebCal.GetDayOfMonth(BirthDate)) Then iAge -= 1
    Return iAge
End Function

为什么不能简化为检查出生日期？

第一行（var year=end.year-start.year-1；）：假设出生日期尚未发生在结束年份。然后检查月份和日期，看看是否发生了；再增加一年。

对闰年情景没有特殊处理。如果不是闰年，你不能创建一个日期（2月29日）作为结束日期，所以如果结束日期是3月1日，而不是28日，生日庆祝活动将被计算在内。下面的函数将将此场景作为普通日期进行描述。

    static int Get_Age(DateTime start, DateTime end)
    {
        var year = end.Year - start.Year - 1;
        if (end.Month < start.Month)
            return year;
        else if (end.Month == start.Month)
        {
            if (end.Day >= start.Day)
                return ++year;
            return year;
        }
        else
            return ++year;
    }

    static void Test_Get_Age()
    {
        var start = new DateTime(2008, 4, 10); // b-date, leap year BTY
        var end = new DateTime(2023, 2, 1); // end date is before the b-date
        var result1 = Get_Age(start, end);
        var success1 = result1 == 14; // true

        end = new DateTime(2023, 4, 10); // end date is on the b-date
        var result2 = Get_Age(start, end);
        var success2 = result2 == 15; // true

        end = new DateTime(2023, 6, 22); // end date is after the b-date
        var result3 = Get_Age(start, end);
        var success3 = result3 == 15; // true

        start = new DateTime(2008, 2, 29); // b-date is on feb 29
        end = new DateTime(2023, 2, 28); // end date is before the b-date
        var result4 = Get_Age(start, end);
        var success4 = result4 == 14; // true

        end = new DateTime(2020, 2, 29); // end date is on the b-date, on another leap year
        var result5 = Get_Age(start, end);
        var success5 = result5 == 12; // true
    }

我花了一些时间研究这个问题，并用这个来计算某人的年龄，以年、月和日为单位。我已经针对2月29日的问题和闰年进行了测试，它似乎奏效了，我希望得到任何反馈：

public void LoopAge(DateTime myDOB, DateTime FutureDate)
{
    int years = 0;
    int months = 0;
    int days = 0;

    DateTime tmpMyDOB = new DateTime(myDOB.Year, myDOB.Month, 1);

    DateTime tmpFutureDate = new DateTime(FutureDate.Year, FutureDate.Month, 1);

    while (tmpMyDOB.AddYears(years).AddMonths(months) < tmpFutureDate)
    {
        months++;

        if (months > 12)
        {
            years++;
            months = months - 12;
        }
    }

    if (FutureDate.Day >= myDOB.Day)
    {
        days = days + FutureDate.Day - myDOB.Day;
    }
    else
    {
        months--;

        if (months < 0)
        {
            years--;
            months = months + 12;
        }

        days +=
            DateTime.DaysInMonth(
                FutureDate.AddMonths(-1).Year, FutureDate.AddMonths(-1).Month
            ) + FutureDate.Day - myDOB.Day;

    }

    //add an extra day if the dob is a leap day
    if (DateTime.IsLeapYear(myDOB.Year) && myDOB.Month == 2 && myDOB.Day == 29)
    {
        //but only if the future date is less than 1st March
        if (FutureDate >= new DateTime(FutureDate.Year, 3, 1))
            days++;
    }

}

要使用最近的年龄计算年龄：

var ts = DateTime.Now - new DateTime(1988, 3, 19);
var age = Math.Round(ts.Days / 365.0);

只是因为我认为最重要的答案不是那么明确：

public static int GetAgeByLoop(DateTime birthday)
{
    var age = -1;

    for (var date = birthday; date < DateTime.Today; date = date.AddYears(1))
    {
        age++;
    }

    return age;
}

对此的简单答案是应用AddYears，如下所示，因为这是唯一一种将年份添加到闰年2月29日的本地方法，并获得普通年份2月28日的正确结果。

有些人认为3月1日是勒普林斯的生日，但.Net和任何官方规则都不支持这一点，也没有常见的逻辑解释为什么一些出生在2月的人应该在另一个月拥有75%的生日。

此外，Age方法可以作为DateTime的扩展添加。由此，您可以以最简单的方式获得年龄：

列表项目

int age=出生日期.age（）；

public static class DateTimeExtensions
{
    /// <summary>
    /// Calculates the age in years of the current System.DateTime object today.
    /// </summary>
    /// <param name="birthDate">The date of birth</param>
    /// <returns>Age in years today. 0 is returned for a future date of birth.</returns>
    public static int Age(this DateTime birthDate)
    {
        return Age(birthDate, DateTime.Today);
    }

    /// <summary>
    /// Calculates the age in years of the current System.DateTime object on a later date.
    /// </summary>
    /// <param name="birthDate">The date of birth</param>
    /// <param name="laterDate">The date on which to calculate the age.</param>
    /// <returns>Age in years on a later day. 0 is returned as minimum.</returns>
    public static int Age(this DateTime birthDate, DateTime laterDate)
    {
        int age;
        age = laterDate.Year - birthDate.Year;

        if (age > 0)
        {
            age -= Convert.ToInt32(laterDate.Date < birthDate.Date.AddYears(age));
        }
        else
        {
            age = 0;
        }

        return age;
    }
}

现在，运行此测试：

class Program
{
    static void Main(string[] args)
    {
        RunTest();
    }

    private static void RunTest()
    {
        DateTime birthDate = new DateTime(2000, 2, 28);
        DateTime laterDate = new DateTime(2011, 2, 27);
        string iso = "yyyy-MM-dd";

        for (int i = 0; i < 3; i++)
        {
            for (int j = 0; j < 3; j++)
            {
                Console.WriteLine("Birth date: " + birthDate.AddDays(i).ToString(iso) + "  Later date: " + laterDate.AddDays(j).ToString(iso) + "  Age: " + birthDate.AddDays(i).Age(laterDate.AddDays(j)).ToString());
            }
        }

        Console.ReadKey();
    }
}

关键日期示例如下：

出生日期：2000-02-29出生日期：2011-02-28年龄：11

输出：

{
    Birth date: 2000-02-28  Later date: 2011-02-27  Age: 10
    Birth date: 2000-02-28  Later date: 2011-02-28  Age: 11
    Birth date: 2000-02-28  Later date: 2011-03-01  Age: 11
    Birth date: 2000-02-29  Later date: 2011-02-27  Age: 10
    Birth date: 2000-02-29  Later date: 2011-02-28  Age: 11
    Birth date: 2000-02-29  Later date: 2011-03-01  Age: 11
    Birth date: 2000-03-01  Later date: 2011-02-27  Age: 10
    Birth date: 2000-03-01  Later date: 2011-02-28  Age: 10
    Birth date: 2000-03-01  Later date: 2011-03-01  Age: 11
}

2012年2月28日晚些时候：

{
    Birth date: 2000-02-28  Later date: 2012-02-28  Age: 12
    Birth date: 2000-02-28  Later date: 2012-02-29  Age: 12
    Birth date: 2000-02-28  Later date: 2012-03-01  Age: 12
    Birth date: 2000-02-29  Later date: 2012-02-28  Age: 11
    Birth date: 2000-02-29  Later date: 2012-02-29  Age: 12
    Birth date: 2000-02-29  Later date: 2012-03-01  Age: 12
    Birth date: 2000-03-01  Later date: 2012-02-28  Age: 11
    Birth date: 2000-03-01  Later date: 2012-02-29  Age: 11
    Birth date: 2000-03-01  Later date: 2012-03-01  Age: 12
}