看看这个：

TimeSpan ts = DateTime.Now.Subtract(Birthdate);
age = (byte)(ts.TotalDays / 365.25);

以下是使用DateTimeOffset和手动数学的答案：

var diff = DateTimeOffset.Now - dateOfBirth;
var sinceEpoch = DateTimeOffset.UnixEpoch + diff;

return sinceEpoch.Year - 1970;

一句话的回答：

DateTime dateOfBirth = Convert.ToDateTime("01/16/1990");
var age = ((DateTime.Now - dateOfBirth).Days) / 365;

这里有一个小的C#代码示例，我总结了一下，请注意边缘情况，特别是闰年，并不是所有上述解决方案都考虑到这些情况。将答案推出来作为DateTime可能会导致问题，因为你可能会在一个特定的月份中投入太多的时间，例如2月的30天。

public string 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 = 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++;
    }

    return "Years: " + years + " Months: " + months + " Days: " + days;
}

这是一个非常适合我的功能。没有计算，非常简单。

    public static string ToAge(this DateTime dob, DateTime? toDate = null)
    {
        if (!toDate.HasValue)
            toDate = DateTime.Now;
        var now = toDate.Value;

        if (now.CompareTo(dob) < 0)
            return "Future date";

        int years = now.Year - dob.Year;
        int months = now.Month - dob.Month;
        int days = now.Day - dob.Day;

        if (days < 0)
        {
            months--;
            days = DateTime.DaysInMonth(dob.Year, dob.Month) - dob.Day + now.Day;
        }

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


        return string.Format("{0} year(s), {1} month(s), {2} days(s)",
            years,
            months,
            days);
    }

这里是一个单元测试：

    [Test]
    public void ToAgeTests()
    {
        var date = new DateTime(2000, 1, 1);
        Assert.AreEqual("0 year(s), 0 month(s), 1 days(s)", new DateTime(1999, 12, 31).ToAge(date));
        Assert.AreEqual("0 year(s), 0 month(s), 0 days(s)", new DateTime(2000, 1, 1).ToAge(date));
        Assert.AreEqual("1 year(s), 0 month(s), 0 days(s)", new DateTime(1999, 1, 1).ToAge(date));
        Assert.AreEqual("0 year(s), 11 month(s), 0 days(s)", new DateTime(1999, 2, 1).ToAge(date));
        Assert.AreEqual("0 year(s), 10 month(s), 25 days(s)", new DateTime(1999, 2, 4).ToAge(date));
        Assert.AreEqual("0 year(s), 10 month(s), 1 days(s)", new DateTime(1999, 2, 28).ToAge(date));

        date = new DateTime(2000, 2, 15);
        Assert.AreEqual("0 year(s), 0 month(s), 28 days(s)", new DateTime(2000, 1, 18).ToAge(date));
    }

只需使用：

(DateTime.Now - myDate).TotalHours / 8766.0

当前日期-myDate=TimeSpan，获取总小时数并除以每年的总小时数，得到确切的年龄/月/日。。。