获取经过的时间跨度的年、月、日 (DateTime)

如何将日期时间选择器值中的年龄显示为年、月、日。例如：

Datetimepicker value = #1/11/2014#
Today = #1/12/2015#.  

最终结果将是“1 年，0 个月，1 天(S)”。但得到这个结果不仅仅是减去DateTime.Year价值观等。有人知道这方面的数学公式或数学计算吗？

这里有一个DateTimeSpan返回一个对象的类型，例如TimeSpan代表两个日期之间经过的年、月、日。它循环遍历时间单位以递增它们，直到较小的日期与较大的日期匹配。然后将所得增量返回到新的DateTimeSpan object.

Public Structure DateTimeSpan

    Private _Years As Integer
    Public ReadOnly Property Years As Integer
        Get
            Return _Years
        End Get
    End Property

    Private _Months As Integer
    Public ReadOnly Property Months As Integer
        Get
            Return _Months
        End Get
    End Property

    Private _Days As Integer
    Public ReadOnly Property Days As Integer
        Get
            Return _Days
        End Get
    End Property

    Private _Hours As Integer
    Public ReadOnly Property Hours As Integer
        Get
            Return _Hours
        End Get
    End Property

    Private _Minutes As Integer
    Public ReadOnly Property Minutes As Integer
        Get
            Return _Minutes
        End Get
    End Property

    Private _Seconds As Integer
    Public ReadOnly Property Seconds As Integer
        Get
            Return _Seconds
        End Get
    End Property

    Private _MilliSeconds As Integer
    Public ReadOnly Property MilliSeconds As Integer
        Get
            Return _MilliSeconds
        End Get
    End Property

    ' the ctor for the result
    Private Sub New(y As Integer, mm As Integer, d As Integer,
                    h As Integer, m As Integer, s As Integer,
                    ms As Integer)
        _Years = y
        _Months = mm
        _Days = d
        _Hours = h
        _Minutes = m
        _Seconds = Seconds
        _MilliSeconds = ms
    End Sub

    ' private time unit tracker when counting
    Private Enum Unit
        Year
        Month
        Day
        Complete
    End Enum

    Public Shared Function DateSpan(dt1 As DateTime, 
                                    dt2 As DateTime) As DateTimeSpan
        ' we dont do negatives
        If dt2 < dt1 Then
            Dim tmp = dt1
            dt1 = dt2
            dt2 = tmp
        End If

        Dim thisDT As DateTime = dt1
        Dim years As Integer = 0
        Dim months As Integer = 0
        Dim days As Integer = 0

        Dim level As Unit = Unit.Year
        Dim span As New DateTimeSpan()

        While level <> Unit.Complete
            Select Case level
                ' add a year until it is larger;
                ' then change the "level" to month
                Case Unit.Year
                    If thisDT.AddYears(years + 1) > dt2 Then
                        level = Unit.Month
                        thisDT = thisDT.AddYears(years)
                    Else
                        years += 1
                    End If

                Case Unit.Month
                    If thisDT.AddMonths(months + 1) > dt2 Then
                        level = Unit.Day
                        thisDT = thisDT.AddMonths(months)
                    Else
                        months += 1
                    End If

                Case Unit.Day
                    If thisDT.AddDays(days + 1) > dt2 Then
                        thisDT = thisDT.AddDays(days)
                        Dim thisTS = dt2 - thisDT
                        ' create a new DTS from the values caluclated
                        span = New DateTimeSpan(years, months, days, thisTS.Hours,
                                                thisTS.Minutes, thisTS.Seconds,
                                    thisTS.Milliseconds)
                        level = Unit.Complete
                    Else
                        days += 1
                    End If
            End Select
        End While

        Return span

    End Function

End Structure

Usage:

Dim dts As DateTimeSpan = DateTimeSpan.DateSpan(#2/11/2010#, #10/21/2013#)
Console.WriteLine("{0} Yrs, {1} Months and {2} Days",
                           dts.Years.ToString, dts.Months.ToString, dts.Days.ToString)

这将给出相同的结果：

Dim dtStart As DateTime = #2/11/2010#
Dim dtEnd As new DateTime(2013, 10, 21)
' this is NOT a date and wont work:
Dim myDt = "2/11/2010"             ' its a string!

Dim dts As DateTimeSpan = DateTimeSpan.DateSpan(dtEnd, dtStart)

Result: 3 Yrs, 8 Months and 10 Days

Notes:
- 它仅适用于正确的DateTime类型，而不是看起来像日期的字符串。使用文字 (#...#) or DateTime变量。当使用DateTimePicker, use .Value not .Text.
- 它不执行负值，因此传递值的顺序并不重要
- 计算时，它增加aDateTime变量所以，它应该正确考虑闰日

这是基于我很久以前在博客中找到的一些 C# 代码（或者甚至可能是来自 SO 答案或问题）。现在找不到引用原文。