Date value subtraction producing wrong error

Question

I am using the below code to show the date difference in Day:Hour:Minute format.

 Function TimeSpan(dt1, dt2) 

    Dim seconds,minutes,hours,days

    If (isDate(dt1) And IsDate(dt2)) = false Then 
        TimeSpan = "00:00:00" 
        Exit Function 
    End If 

    seconds = Abs(DateDiff("S", dt1, dt2)) 
    minutes = seconds \ 60 
    hours = minutes \ 60 
    days  = hours \ 24
    minutes = minutes mod 60 
    seconds = seconds mod 60 
    days    = days    mod 24 

    if len(hours) = 1 then hours = "0" & hours 

    TimeSpan = days& ":" & _ 
        RIGHT("00" & hours , 2) & ":" & _ 
        RIGHT("00" & minutes, 2) 
End Function 

But it is not producing expected values for some cases.

  D1=#9/24/2012  8:09:15 AM# and D2=#9/25/2012  8:09:15 AM# gives correct data like 1:24:00 whereas below are producing error when working with VBScript and Excel.
  D1=#9/5/2012  8:45:43 AM# and D2=#9/25/2012  8:45:43 AM# result=0.888888888888889
  D1=#9/6/2012  8:29:34 AM# and D2=#9/17/2012  8:59:36 AM# result=0.503125

Can you explain why so?

Thanks

Answer 1

Try my answer from an earlier post in your UDF as the following: This answer is in VBA

Please declare all variables and force yourself to declare by adding option explicit :)

option explicit
Function TimeSpan(dt1 As Date, dt2 As Date) As String
Dim dtTemp As Date

    Application.ScreenUpdating = False
        If (IsDate(dt1) And IsDate(dt2)) = False Then
            TimeSpan = "00:00:00"
            Exit Function
        End If

        If dt2 < dt1 Then
            dtTemp = dt2
            dt2 = dt1
            dt1 = dt2
        End If
        '-- since you only had days, I have put up to days here. 
        '-- if you require months, years you may use yy:mm:dd:hh:mm:ss
        '-- which is pretty self-explainatory ;)
        TimeSpan = Application.WorksheetFunction.Text((dt2 - dt1), "dd:hh:mm:ss")

    Application.ScreenUpdating = False
End Function

UDF Output:

But I really suggest you to use Excel sheet functions if you have the freedom and possibility to do so.

---

If date difference is more than 31 days

Then use the solution as per this article Incorporate the DateDiff to the UDF.

Answer 2

Be aware I'm more used to write VBA, so you might need to tweak here and there.

Alternatively you could just subtract the two dates from eachother as numerical value:

Dim dblDateDiff as Double
dblDateDiff = Abs(dt2 - dt1)

Now the Timespan would be (dont use "d" as that would not include months and years that could have passed):

Timespan = Int(dblDateDiff) & ":" & Hour(dblDateDiff) & ":" & Minute(dblDateDiff)

If the direction (positive or negative) of the Timespan is relevant you could change the last line into:

Timespan = Sgn(dblDateDiff) * Int(dblDateDiff) & ":" & Hour(dblDateDiff) & ":" & Minute(dblDateDiff)

For your time formatting issue either:

1. Set the number format of the output cell to Text, or

2. Add a single quote in front of the rest of the string:

    Timespan = "'" & Sgn(dblDateDiff) * Int(dblDateDiff) & ":" & Hour(dblDateDiff) & ":" & Minute(dblDateDiff)