Time Calculation in Excel VBA - vba

Question

I am getting time as 23300000 i.e. hhMMssmm format as string
and I want to calculate difference of such two values.
Here hh is hours, MM is minutes, ss is seconds, and mm is 60th of second.
Using VBA for Excel 2003

Answer 1

This UDF will return the absolute value of the difference in seconds
Public Function tDiff(s1 As String, s2 As String) As Double
'
' calculates the absolute value of the differences
' returns the answer in seconds
'
Dim hrs As Double, mins As Double, secs As Double, sixt As Double
Dim tVal1 As Double, tVal2 As Double
hrs = CDbl(Mid(s1, 1, 2)) * 60 * 60
mins = CDbl(Mid(s1, 3, 2)) * 60
secs = CDbl(Mid(s1, 5, 2))
sixt = CDbl(Mid(s1, 7, 2)) / 60
tVal1 = hrs + mins + secs + sixt
hrs = CDbl(Mid(s2, 1, 2)) * 60 * 60
mins = CDbl(Mid(s2, 3, 2)) * 60
secs = CDbl(Mid(s2, 5, 2))
sixt = CDbl(Mid(s2, 7, 2)) / 60
tVal2 = hrs + mins + secs + sixt
If tVal1 > tVal2 Then
tDiff = tVal1 - tVal2
Else
tDiff = tVal2 - tVal1
End If
End Function

Answer 2

How about something like this:
Public Sub test()
Dim ms1 As Double
Dim ms2 As Double
ms1 = ToSeconds(23142700)
ms2 = ToSeconds(23311500)
Debug.Print "Difference between dates in seconds: " & ms2 - ms1
End Sub
Public Function ToSeconds(number As Long) As Double
Dim hh As Long
Dim mm As Long
Dim ss As Long
Dim ms As Long
ms = (number Mod (100 ^ 1)) / (100 ^ 0)
ss = (number Mod (100 ^ 2) - ms) / (100 ^ 1)
mm = (number Mod (100 ^ 3) - ss * (100 ^ 1) - ms) / (100 ^ 2)
hh = (number Mod (100 ^ 4) - mm * (100 ^ 2) - ss * (100 ^ 1) - ms) / (100 ^ 3)
ToSeconds = ms * 1 / 60 + ss + mm * 60 + hh * 60 * 60
End Function
The ToSeconds() function converts your number to seconds, and you can do your calculations based on that.

Answer 3

While this solution may not be as short as the others, I believe it is very easy to understand. Not everything here may be necessary, but you may find some of it useful in the future.
The run sub routine allows you to run the test function with your specified values.
The test function tests the timeDiff & timeSum logic.
The timeDiff function finds the time-difference between t1 and t0.
The timeSum function finds the time-sum of t1 and t0.
The asDuration function removes the AM/PM suffix from a time value.
The asMilitary function converts 12-hour format to 24 hour-format.
The concat function I created to more easily concatenate strings.
Sub Main() 'Run Test
MsgBox Test("0:29:0", "23:30:0")
End Sub
Function Test(startT As Date, endT As Date) 'Test timeDiff & timeSum logic
Dim nextShift As Date, prevShift As Date, hours As Date
hours = timeDiff(endT, startT)
prevShift = timeDiff(startT, "0:30:0")
nextShift = timeSum("0:30:0", endT)
Test = concat("Start -", startT, "", "End - ", endT, "", "Duration -", asDuration(hours), "", "Next Shift: ", nextShift, "", "Prev Shift: ", prevShift)
End Function
Function timeDiff(t1 As Date, t0 As Date) As Date 'Return Time1 minus Time0
Dim units(0 To 2) As String
units(0) = Hour(t1) - Hour(t0)
units(1) = Minute(t1) - Minute(t0)
units(2) = Second(t1) - Second(t0)
If units(2) < 0 Then
units(2) = units(2) + 60
units(1) = units(1) - 1
End If
If units(1) < 0 Then
units(1) = units(1) + 60
units(0) = units(0) - 1
End If
units(0) = IIf(units(0) < 0, units(0) + 24, units(0))
timeDiff = Join(units, ":")
End Function
Function timeSum(t1 As Date, t0 As Date) As Date 'Return Time1 plus Time0
Dim units(0 To 2) As String
units(0) = Hour(t1) + Hour(t0)
units(1) = Minute(t1) + Minute(t0)
units(2) = Second(t1) + Second(t0)
If units(2) >= 60 Then
units(2) = units(2) Mod 60
units(1) = units(1) + 1
End If
If units(1) >= 60 Then
units(1) = units(1) Mod 60
units(0) = units(0) + 1
End If
units(0) = IIf(units(0) >= 24, units(0) Mod 24, units(0))
timeSum = Join(units, ":")
End Function
Function asDuration(time As Date) As String 'Display as duration; Remove AM/PM suffix from time
time = asMilitary(time)
asDuration = Left(time, Len(time))
End Function
Function asMilitary(time As Date) As String 'Convert 12-hour format to 24-hour-format
asMilitary = Hour(time) & ":" & Minute(time) & ":" & Second(time)
End Function
Function concat(ParamArray var() As Variant) As String 'Return arguments of function call concatenated as a single string
For Each elem In var()
concat = IIf(elem <> "", concat & elem & " ", concat & vbNewLine)
Next
End Function