vba excel datediff calculates different results - excel

Question

I am trying to calculate time difference in hours between two times.
But i am not getting the exspected result, as a matter of fact the same function
throws me two different results.
time between 14:22:00 and 22:57:48 should come as 8 hours 35 minutes and 48 sec.
However i get two different numbers.
If i store the value as a date i get 14:19:12
If i calculate in a msgbox on the go i get 8,5966...
Neither is correct, or maybe it is using some sort of format i am unaware of.
Screenshot shows both the msgbox and the storage test.
Also posted in exspected result.
Any suggestions?
Public Sub DDtest()
Dim EDay As Date
Dim ETime As Date
Dim DtgA As Date
EDay = Format(CDate(Replace(Worksheets("Data2020").Range("E2").Value, ".", "/")), "dd-mmm-yyyy")
ETime = Format(Worksheets("Data2020").Range("F2"), "hh:mm:ss")
DtgA = EDay + ETime
Dim EDay2 As Date
Dim ETime2 As Date
Dim DtgB As Date
EDay2 = Format(CDate(Replace(Worksheets("Data2020").Range("E3").Value, ".", "/")), "dd-mmm-yyyy")
ETime2 = Format(Worksheets("Data2020").Range("F3"), "hh:mm:ss")
DtgB = EDay2 + ETime2
Dim result As Date
result = Format(DateDiff("s", DtgA, DtgB) / (60 * 60), "hh:mm:ss")
MsgBox "Date 1:" & DtgA & vbNewLine & "Date 2:" & DtgB & vbNewLine & vbNewLine & DateDiff("s", DtgA, DtgB) / (60 * 60) & vbNewLine & result
End Sub

Answer 1

DateDiff("s", DtgA, DtgB) / (60 * 60) will return a decimal value, in this case is 8.59666666666667 hours
When you apply Format to convert it into hh:mm:ss, the value 8.59666666666667 is not being treated as hours. Excel thinks it's a decimal value that must be converted into date, and it's being treated as days.
In Excel, Dates are always numbers. Integer part is the date itself, while decimal part is time, a part of that day but not the day itself.
First day Excel can use is 01/01/1900 and numeric value is 1, 2 is 02/01/1900 and so on.
So Excel thinks 8.59666666666667 is 08/01/1900 14:19:12
If you divide those hours between 24, you will get the right result:
result = Format(DateDiff("s", DtgA, DtgB) / (60 * 60) / 24, "hh:mm:ss")
You get this:
Note the first value is decimal value and the second one is formatted as hh:mm:ss. But both of them show the same value, with different format.
UPDATE: Actually, if you force your dates values to make a difference of 8 and a half hours exactly, you will see perfectly how Excel works. Same value but with different format.
I've forced dates to be 12/12/2019 14:22:00 and 12/12/2019 22:52:00 and I get this:
Exactly 8 hours and a half, but first in decimal and second is format hh:mm:ss.

Answer 2

Why are you formatting before calculation? If cell value is date formatting doesn't meter.
date & time = 441040.598611111111111
Sub calcDatediff()
date1 = Worksheets("masterdata").Range("C11")
time1 = Worksheets("masterdata").Range("D11")
date2 = Worksheets("masterdata").Range("C12")
time2 = Worksheets("masterdata").Range("D12")
dtime1 = date1 + time1
dtime2 = date2 + time2
difftime = Format(dtime2 - dtime1, "HH:mm:ss", vbMonday, vbFirstFourDays)
End Sub