Replace periods with commas ends up with period deletion - excel

Question

This is my first month with VBA and I've overcome so many obstacles and reduced walls of code with loops, made code pretty much uncrashable, even when user using macro doesn't know what he/she is doing, but I am stuck with this:
If i = 1 Or i = 2 Then
Columns("F:F").Select
Selection.Replace ".", ","
Selection.NumberFormat = "dd\/mm\/yyyy hh:mm:ss"
End If
For some reason the result of replacement of:
438595.73402778 is this 43859573402778
I tried different variations from recording the macro to gradually simplifying the code and ended up with above. Always same result. What am I missing here?
The code is kind of complex, because I have to take data from 6 temporary workbooks into 4 sheets, secure it, depending on user login etc. It works great, but I thought, let's make it even better, because 3 out of those 6 qlikview workbooks have incorrect format in 1 of 4 time tracking columns.
It's kind of sad that I had to write my first post for such thing

Answer 1

I assume your current data is actually string data looking like numeric values. If column F is formatted to General and these "string" numbers appear, then you could change that around using Range.TextToColumns. For example:
Sub Test()
Dim lr As Long, rng As Range
With Sheet1
'Get last used row of column F and set rng
lr = .Cells(.Rows.Count, 6).End(xlUp).Row
Set rng = .Range("F2:F" & lr)
'Replace dot with comma and change to numeric
rng.TextToColumns Destination:=Range("F2"), DataType:=xlFixedWidth, DecimalSeparator:=".", ThousandsSeparator:=","
rng.NumberFormat = "dd\/mm\/yyyy hh:mm:ss"
End With
End Sub

Answer 2

Seems like you have different decimal separator settings in Excel files.
Go to Options-> extended-> use systems decimal separator.
This option may be off on some workbooks and ,is set as decimal separator.
to fix:
If Application.International(xlDecimalSeparator) = "," Then
MsgBox "Wrong decimal separator(,)!!"
Application.UseSystemSeparators = True
End If
If you want to output dot but leave comma the separator use
With ThisWorkBook.WorkSheet("Sheet1")
MsgBox Str( .Range("A1"))
End With
See Using VBA to detect which decimal sign the computer is using