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

Question

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 NoOfdays <= 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

Answer 1

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.

Answer 2

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

Answer 3

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);

Answer 4

You can subtract DateTime objects to get a TimeSpan object:
DateTime startDate = GetStartDate();
DateTime endDate = GetEndDate();
TimeSpan duration = endDate - startDate;

Answer 5

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

Answer 6

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)