VBA - Find date within text containing format 'DDMMYYYY' - excel

Question

I've scanned and found many similar answers to my question although none of them are quite ticking the boxes, so I'll explain what I'm after and hopefully it makes sense:
I have imported data into an excel spreadsheet (working with 2007) from a TXT, which contains various dates (all in the format DDMMYYYY).
What I'm trying to do is create a sub routine which finds any dates in this format and subsequently decreases the date by 1 year.
The dates are within a range when the TXT has been imported (in this instance, the first 2 dates appear under range A6) so ideally I would like to specify that range because I don't necessarily want to decrease all dates present in the TXT.
For example, here's the incorrect code which I am sure needs some serious tweaking!
Cells.Replace What:="Dates", Replacement:="Dates-1", LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False, SearchFormat:=DDMMYYYY, _
ReplaceFormat:=False
I gather there is some prior definition that needs to be carried out before anything like the above code would work but if there is anyone who can help, I'd appreciate it!
Many thanks,
Robin.

Answer 1

I do not believe any tweak will allow your code to achieve the effect you seek. I cannot give a definitive answer because I do not quite believe your description. I hope the information below will allow you to investigate your data and develop an appropriate solution.
You are not, as far as I know, using SearchFormat correctly. You need something like this:
With Application.FindFormat
.Font.Bold = True
End With
Set Rng = .Find(. . . SearchFormat = True . . .)
The VBA Editor’s Help for Find states: “SearchFormat Optional Variant. The search format.” but gives no example to show what that means. I cannot find an example of using the find format facility that is not in the above style. That is: you use FindFormat to specify the format(s) of interest and set SearchFormat to True to indicate that those formats are to be searched for.
You could try:
With Application.FindFormat
.NumberFormat = "DDMMYYYY"
End With
I have not tried this and I cannot find any documentation that explains what format types can be searched for. If this works, it will almost certainly be faster and easier than anything based on the following information.
For Excel to import a string within a text file as a Date, it must:
Recognise the string as a date.
Convert that string to a number.
Store that number with a number format that indicates it is a date.
Excel stores dates as the number of days since 1/1/1900. For example, “21 August 2015” will be stored as 42238 with a number format of “dd mmmm yyyy”. There is nothing about the cell value that says it’s a date. You can enter the cell value as 42238 and later set the number format to “dd mmm yy” and the value will display as “21 Aug 15”.
Your description implies the dates are held in the text file as eight-digit values which Excel recognises as dates and therefore sets the number format to "DDMMYYYY". I have never managed to get Excel to recognise eight-digit values as dates. If you have succeeded, I would like to know how.
My best suggestion is:
For Each CellCrnt in RngImport
If CellCrnt.NumberFormat = "ddmmyyy" Then
' Add year to date
End If
Next
Extension
If you perform the actions I requested in the comment against your question, we should be able to identify the type of the values you wish to locate and modify. This extension explains how you might use that information.
In my earlier code I used RngImport to represent the Range of the imported data. One of your remarks makes me wonder: do you know how to initialise that Range?
Do we have to search the entire Range for these “dates”? That is, are there scattered across the data or are they restricted to a single column? The final code will be faster if we do not have to examine every cell.
My guess is we will need something like:
If IsDate(Mid(CellValue,1,2) & "/" & Mid(CellValue,3,2) & "/" & Mid(CellValue,5,4)) Then
to convert “ddmmyyyy” to “dd/mm/yyyy” and then test the new string to be a date.

Answer 2

Here is my suggestion:
Sub OneYearEarlier()
Dim c As Range
Dim dt As Date
For Each c In Selection
If c.NumberFormatLocal = "TT.MM.JJJJ" Then
dt = DateAdd("yyyy", -1, c.Value)
c.Value = dt
End If
Next c
End Sub
Firstly, I think you have to handle the cell value as a Date data type, not as a string. This will avoid overflow or underflow which might occur if not decreasing by one year but some other time interval, e.g. one month.
Secondly, as mentioned by others you cannot reliably detect that a number is a date in XL. My code uses
- only cells which you have selected beforehand (e.g. one column)
- only cells with a date format
I use NumberFormatLocal here so that the format string is identical to the one which you see in the format dialog/"custom format". But this is not really critical here, just a convenience.
I really dislike having to use both the 'internal' format string "yyyy" and the localized format string "JJJJ" but that's the way DateAdd wants it.

Answer 3

You can always create your own RegEx function to simplify:
Function RegEx(Target As String, RegExpression As String, _
Optional ReplaceString As String, Optional xIgnoreCase As Boolean, _
Optional xGlobal As Boolean, Optional xMultiLine As Boolean)
Dim regexOne As Objectv
Set regexOne = New RegExp
regexOne.Pattern = RegExpression
If xIgnoreCase Then regexOne.IgnoreCase = xIgnoreCase
If xGlobal Then regexOne.Global = xGlobal
If xMultiLine Then regexOne.MultiLine = xMultiLine
If regexOne.Test(Target) Then
If IsMissing(ReplaceString) Then
RegEx = regexOne.Execute(Target)
Else
RegEx = regexOne.Replace(Target, ReplaceString)
End If
End If
End Function
You could use this for your problem in this way:
Function fDateAdd(SearchTextas Date, DateUnit as String, ModAmount as Interger)
FoundText = RegEx(SearchText, "######")
Do
If IsDate(FoundText) And (Mid(FoundText, 5, 2)="19" Or Mid(FoundText, 5, 2)="20") Then
ReplaceWithText = DateAdd(DateUnit, ModAmount, CDate(FoundText))
fDateAdd = Replace(SearchText, FoundText, ReplaceWithText)
End If
FoundText = RegEx(SearchText, "######")
Loop While FoundText <> ""
End Function