Finding String and Reformatting Accordingly - vbscript

Question

I've been working on a VBScript that finds all files with a specific extension, .dat, searches for a specific pattern, "Date Due:\d{8}", and shifts the string around in a specific format.
I am having two problems with the below code:
It is not reading the first line. Whenever I run the script it seems to jump immediately to the second line.
It is only using the first pattern it finds and replaces the following patterns with the first pattern in the newly formatted manner.
I hope this makes sense, it's a very specific script, but I am hoping for some help understanding the problem here.
Below is my code:
Set fso = CreateObject("Scripting.FileSystemObject")
'newtext = vbLf & "Date Due:" & sub_month & sub_day & sub_year 'the text replacing Date Due:
'the purpose of this script is to format the date after Date Due:, which is currently formatted as YYYYMMDD, to MM/DD/YYYY
'example: Date Date:20180605 should be Date Due:06/05/2018
Set re = New RegExp
re.Pattern = "(\nDate Due:\d{8})" 'Looking for line, Date Due: followed by 8 digits
Dim sub_str 'substring of date due, returns the 8 digits aka the date 12345678
Dim sub_month
Dim sub_day
Dim sub_year
Dim concat_full
re.Global = False
re.IgnoreCase = True
For Each f In fso.GetFolder("C:\Users\tgl\Desktop\TestFolder\").Files
If LCase(fso.GetExtensionName(f.Name)) = "dat" Then
text = f.OpenAsTextStream.ReadAll
sub_str = Mid(text, 10, 8) 'substring of the full line, outputs the 8 digit date
sub_month = Mid(sub_str, 5, 2) 'substring of the date, outputs the 2 digit month
sub_day = Mid(sub_str, 7, 2) 'substring of the date, outputs the 2 digit day
sub_year = Mid(sub_str, 1, 4) 'substring of the date, outputs the four digit year
newtext = vbLf & "Date Due:" & sub_month & "/" & sub_day & "/" & sub_year 'replaces the text pattern defined above and concatenates the substrings with slashes
'concat_full = (sub_month & sub_day & sub_year)
f.OpenAsTextStream(2).Write re.Replace(text, newtext)
End If
Next
EDIT: When changing re.Global to True it replaces each line with the one found pattern. It should be using each found pattern as it's own and not the first one it finds.

Answer 1

Make your regular expression more specific and use capturing groups for extracting the relevant submatches:
re.Pattern = "(\nDate Due:)(\d{4})(\d{2})(\d{2})"
then replace the matches like this:
re.Replace(text, "$1$4/$3/$2")
$1 through $4 in the replacement string are backreferences to the capturing groups in the pattern (i.e. they're replaced with the respective captured substring).