Question

I need to return the exact difference between two dates in the form of a string.

If the dates are 01-FEB-2012 and 01-FEB-2014, the function should return “2 years“.
If the dates are 01-FEB-2012 and 01-MAR-2014, the function should return “25 months“.
If the difference is not in exact years or months, it should return the difference in days.

I do not want to use DateDiff from the Visual Basic namespace so the code is portable to C#.

Answer 1

'Assuming d1 < d2    
Public Function GetDateDiff(d1 as DateTime, d2 As DateTime) As String

    If d1.Day = d2.Day Then
        Dim yearDiff As Integer = d2.Year - d1.Year
        If d1.Month = d2.Month Then
            'Only year differs
            Return yearDiff & " years"
        Else
            'Month and year differs
            Dim monthDiff As Integer = d2.Month - d1.Month
            Return (yearDiff * 12 + monthDiff) & " months"
        End If
    Else
        Return (d2-d1).TotalDays & " days"
    End If
End Function