How to Calculate Two Different Dates like 2 years, 5 months

I want to calculate the difference between two dates and want to convert it like 2 years, 5 months or only 3 months, or 2 days according to the difference considering all months are 30 days...

For example;

From and including: Mar 12, 2009 To, but not including : Nov 26, 2011

The output must be : 2 years, 8 months, 14 days excluding the end date.

Another example;

Start: Jan 26, 2010 End: Feb 15, 2010

Output: 20 days from the start date to the end date, but not including the end date

I can calculate the difference as month, day or hour with Datediff but the question is how to convert it to years, months and dates. It's quite complicated actually as we don't know how many days there are between two months (30,31 maybe 28 days)

I use this Classic ASP code to convert the difference but there are lot's of disadvantages.

Function Convert_Date_to_Text(tarih1,tarih2,useDates)

if (tarih1<>"" AND tarih2<>"") then
    if Tarih_Araligi_Belirle(tarih1,tarih2,"day")>0 then

        Date1_Year          = Year(tarih1) 
        Date1_Month         = Month(tarih1) 
        Date1_Day           = Day(tarih1)
        Date2_Year          = Year(tarih2)
        Date2_Month         = Month(tarih2)
        Date2_Day           = Day(tarih2)

        If (Date1_Month = 12) and (Date1_Day = 31) and 
                    (Date2_Month = 1) and (Date2_Day = 1) Then 
            NoOfyears       = Date2_Year - Date1_Year - 1 
            NoOfmonths      = 0
            NoOfdays        = 1
        Else 
            NoOfyears       = Date2_Year - Date1_Year 
            NoOfmonths      = Date2_Month - Date1_Month
            NoOfdays        = Date2_Day - Date1_Day 
        End If

        If NoOfyears = 1 Then 
            FormatString        = "1 year "
        Else If NoOfyears <= 0 then
            FormatString        = ""
        Else
            FormatString        = CStr(NoOfyears) & " years "
        End If:End If

        If NoOfmonths = 1 Then 
            FormatString        = FormatString & "1 month" 
        Else If NoOfmonths <= 0 then
            FormatString        = FormatString
        Else
            FormatString        = FormatString & CStr(NoOfmonths) & " months "
        End If:End If

        if useDates=1 then
            If NoOfdays = 1 Then 
                FormatString        = FormatString & "1 day" 
            Else If NoOfd开发者_StackOverflow中文版ays <= 0 Then
                FormatString        = FormatString
            Else     
                FormatString        = FormatString & CStr(NoOfdays) & " days"
            End If:End If
        end if

    end if  
end if

Convert_Date_to_Text        =   FormatString

     End Function

This web site calculates the difference perfectly. TimeAndDate.Com

Note: I'm using Classic ASP for several reasons (Company limitations). Sorry for this but I need an ASP function. It looks like TimeSpan doesn't exist in ASP :(

Kind Regards

If you can convert the input strings to DateTime variables, you can try something like this:

DateTime starTime = //something;
DateTime endTime = //something;
TimeSpan oneDay = new TimeSpan(1, 0, 0, 0); //creates a timespan of 1 day
TimeSpan deltaTime = (endTime - startTime) - oneDay;

I would asume asp has the DateTime and TimeSpan variable types.

Here's a function I have used in the past. If you test it, I think you'll find it accurate. Here's where I got it from.

Function YearsMonthsDays(Date1 As Date, Date2 As Date, Optional ShowAll As _
    Boolean = False, Optional Grammar As Boolean = True)

     ' This function returns a string "X years, Y months, Z days" showing the time
     ' between two dates.  This function may be used in any VBA or VB project

     ' Date1 and Date2 must either be dates, or strings that can be implicitly
     ' converted to dates.  If these arguments have time portions, the time portions
     ' are ignored. If Date1 > Date2 (after ignoring time portions), the function
     ' returns an empty string

     ' ShowAll indicates whether all portions of the string "X years, Y months, Z days"
     ' are included in the output.  If ShowAll = True, all portions of the string are
     ' always included.  If ShowAll = False, then if the year portion is zero the year
     ' part of the string is omitted, and if the year portion and month portion are both
     ' zero, than both year and month portions are omitted.  The day portion is always
     ' included, and if at least one year has passed then the month portion is always
     ' included

     ' Grammar indicates whether to test years/months/days for singular or plural

     ' By definition, a "full month" means that the day number in Date2 is >= the day
     ' number in Date1, or Date1 and Date2 occur on the last days of their respective
     ' months. A "full year" means that 12 "full months" have passed.

     ' In Excel, this function is an alternative to the little-known DATEDIF.  DATEDIF
     ' usually works well, but can create strange results when a date is at month end.
     ' Thus, this formula:

     '       =DATEDIF(A1,B1,"y") & " years, " & DATEDIF(A1,B1,"ym") & " months, " &
     '       DATEDIF(A1,B1,"md") & " days"

     ' will return "0 years, 1 months, -2 days" for 31-Jan-2006 and 1-Mar-2006.
     ' This function will return "0 years, 1 month, 1 day"

    Dim TestYear As Long, TestMonth As Long, TestDay As Long
    Dim TargetDate As Date, Last1 As Date, Last2 As Date

     ' Strip time portions
    Date1 = Int(Date1)
    Date2 = Int(Date2)

     ' Test for invalid dates
    If Date1 > Date2 Then
        YearsMonthsDays = ""
        Exit Function
    End If

     ' Test for whether the calendar year is the same
    If Year(Date2) > Year(Date1) Then

         ' Different calendar year.

         ' Test to see if calendar month is the same.  If it is, we have to look at the
         ' day to see if a full year has passed
        If Month(Date2) = Month(Date1) Then
            If Day(Date2) >= Day(Date1) Then
                TestYear = DateDiff("yyyy", Date1, Date2)
            Else
                TestYear = DateDiff("yyyy", Date1, Date2) - 1
            End If

             ' In this case, a full year has definitely passed
        ElseIf Month(Date2) > Month(Date1) Then
            TestYear = DateDiff("yyyy", Date1, Date2)

             ' A full year has not passed
        Else
            TestYear = DateDiff("yyyy", Date1, Date2) - 1
        End If

         ' Calendar year is the same, so a full year has not passed
    Else
        TestYear = 0
    End If

     ' Test to see how many full months have passed, in excess of the number of full
     ' years
    TestMonth = (DateDiff("m", DateSerial(Year(Date1), Month(Date1), 1), _
    DateSerial(Year(Date2), Month(Date2), 1)) + IIf(Day(Date2) >= _
    Day(Date1), 0, -1)) Mod 12

     ' See how many days have passed, in excess of the number of full months.  If the day
     ' number for Date2 is >= that for Date1, it's simple
    If Day(Date2) >= Day(Date1) Then
        TestDay = Day(Date2) - Day(Date1)

         ' If not, we have to test for end of the month
    Else
        Last1 = DateSerial(Year(Date2), Month(Date2), 0)
        Last2 = DateSerial(Year(Date2), Month(Date2) + 1, 0)
        TargetDate = DateSerial(Year(Date2), Month(Date2) - 1, Day(Date1))
        If Last2 = Date2 Then
            If TestMonth = 11 Then
                TestMonth = 0
                TestYear = TestYear + 1
            Else
                TestMonth = TestMonth + 1
            End If
        Else
            TestDay = DateDiff("d", IIf(TargetDate > Last1, Last1, TargetDate), Date2)
        End If
    End If

    If ShowAll Or TestYear >= 1 Then
        YearsMonthsDays = TestYear & IIf(TestYear = 1 And Grammar, " year, ", _
        " years, ") & TestMonth & IIf(TestMonth = 1 And Grammar, " month, ", _
        " months, ") & TestDay & IIf(TestDay = 1 And Grammar, " day", " days")
    Else
        If TestMonth >= 1 Then
            YearsMonthsDays = TestMonth & IIf(TestMonth = 1 And Grammar, " month, ", _
            " months, ") & TestDay & IIf(TestDay = 1 And Grammar, " day", " days")
        Else
            YearsMonthsDays = TestDay & IIf(TestDay = 1 And Grammar, " day", " days")
        End If
    End If

End Function

How about this? (no TimeSpan but not sure if classic asp compatible)

DateTime dateTime1 = new DateTime(2003,2,2);
DateTime dateTime2 = new DateTime(2001,1,1);

int daysDiff = dateTime1.Day - dateTime2.Day;
int monthsDiff = dateTime1.Month - dateTime2.Month;
int yearsDiff = dateTime1.Year - dateTime2.Year;

if (daysDiff < 0)
{
    daysDiff += DateTime.DaysInMonth(dateTime1.Year, dateTime1.Month);
    monthsDiff--;
}

if (monthsDiff < 0)
{
    monthsDiff += 12;
    yearsDiff--;
}

Console.WriteLine(daysDiff);
Console.WriteLine(monthsDiff);
Console.WriteLine(yearsDiff);

You can subtract DateTime objects to get a TimeSpan object:

DateTime startDate = GetStartDate();
DateTime endDate = GetEndDate();
TimeSpan duration = endDate - startDate;

This article includes a DateDiff class:

// ----------------------------------------------------------------------
public void DateDiffSample()
{
  DateTime date1 = new DateTime( 2009, 11, 8, 7, 13, 59 );
  Console.WriteLine( "Date1: {0}", date1 );
  // > Date1: 08.11.2009 07:13:59
  DateTime date2 = new DateTime( 2011, 3, 20, 19, 55, 28 );
  Console.WriteLine( "Date2: {0}", date2 );
  // > Date2: 20.03.2011 19:55:28

  DateDiff dateDiff = new DateDiff( date1, date2 );

  // differences
  Console.WriteLine( "DateDiff.Years: {0}", dateDiff.Years );
  // > DateDiff.Years: 1
  Console.WriteLine( "DateDiff.Quarters: {0}", dateDiff.Quarters );
  // > DateDiff.Quarters: 5
  Console.WriteLine( "DateDiff.Months: {0}", dateDiff.Months );
  // > DateDiff.Months: 16
  Console.WriteLine( "DateDiff.Weeks: {0}", dateDiff.Weeks );
  // > DateDiff.Weeks: 70
  Console.WriteLine( "DateDiff.Days: {0}", dateDiff.Days );
  // > DateDiff.Days: 497
  Console.WriteLine( "DateDiff.Weekdays: {0}", dateDiff.Weekdays );
  // > DateDiff.Weekdays: 71
  Console.WriteLine( "DateDiff.Hours: {0}", dateDiff.Hours );
  // > DateDiff.Hours: 11940
  Console.WriteLine( "DateDiff.Minutes: {0}", dateDiff.Minutes );
  // > DateDiff.Minutes: 716441
  Console.WriteLine( "DateDiff.Seconds: {0}", dateDiff.Seconds );
  // > DateDiff.Seconds: 42986489

  // elapsed
  Console.WriteLine( "DateDiff.ElapsedYears: {0}", dateDiff.ElapsedYears );
  // > DateDiff.ElapsedYears: 1
  Console.WriteLine( "DateDiff.ElapsedMonths: {0}", dateDiff.ElapsedMonths );
  // > DateDiff.ElapsedMonths: 4
  Console.WriteLine( "DateDiff.ElapsedDays: {0}", dateDiff.ElapsedDays );
  // > DateDiff.ElapsedDays: 12
  Console.WriteLine( "DateDiff.ElapsedHours: {0}", dateDiff.ElapsedHours );
  // > DateDiff.ElapsedHours: 12
  Console.WriteLine( "DateDiff.ElapsedMinutes: {0}", dateDiff.ElapsedMinutes );
  // > DateDiff.ElapsedMinutes: 41
  Console.WriteLine( "DateDiff.ElapsedSeconds: {0}", dateDiff.ElapsedSeconds );
  // > DateDiff.ElapsedSeconds: 29

  // description
  Console.WriteLine( "DateDiff.GetDescription(1): {0}", dateDiff.GetDescription( 1 ) );
  // > DateDiff.GetDescription(1): 1 Year
  Console.WriteLine( "DateDiff.GetDescription(2): {0}", dateDiff.GetDescription( 2 ) );
  // > DateDiff.GetDescription(2): 1 Year 4 Months
  Console.WriteLine( "DateDiff.GetDescription(3): {0}", dateDiff.GetDescription( 3 ) );
  // > DateDiff.GetDescription(3): 1 Year 4 Months 12 Days
  Console.WriteLine( "DateDiff.GetDescription(4): {0}", dateDiff.GetDescription( 4 ) );
  // > DateDiff.GetDescription(4): 1 Year 4 Months 12 Days 12 Hours
  Console.WriteLine( "DateDiff.GetDescription(5): {0}", dateDiff.GetDescription( 5 ) );
  // > DateDiff.GetDescription(5): 1 Year 4 Months 12 Days 12 Hours 41 Mins
  Console.WriteLine( "DateDiff.GetDescription(6): {0}", dateDiff.GetDescription( 6 ) );
  // > DateDiff.GetDescription(6): 1 Year 4 Months 12 Days 12 Hours 41 Mins 29 Secs
} // DateDiffSample

Dim intYears
Dim intMonths
Dim intDays

Dim strDate1
Dim strDate2

Dim strAnswer

strDate1 = "01/26/2010"
strDate2 = "02/15/2010"

intYears  = DateDiff("yyyy",strDate1,strDate2)
intMonths = DateDiff("m",strDate1,strDate2)
intDays   = DateDiff("d",strDate1,strDate2)

strAnswer = ""
if intYears > 0 then 
  strAnswer = strAnswer &  CStr(intYears) & "years "
end if
if intMonths > 0 then 
  strAnswer = strAnswer &  CStr(intMonths) & "months"
end if
if intDays > 0 then 
  strAnswer = strAnswer &  CStr(intDays) & "days"
end if

Response.Write("The difference between these two dates is " & strAnswer)