excel - Date formats/values change when file is opened programmatically

Question

I have .csv file which is a time series of daily data, with several data points associated with each date.

When I manually open the file, the dates open correctly, as the date format dd/mm/yyyy.

When I open the file programmatically, the dates up to the 12th of each month are opened as mm/dd/yyyy, although the format remains dd/mm/yyyy (e.g. the 1st of July 1983 (1/7/1983), would be opened as the 7th of January 1983 (7/1/1983) - this isn't just a formatting issue, the Julian Date (days since 1 Jan 1901) associated with these dates also changes), and the dates after the 12th of each month are opened correctly, although as text rather than a date.

The data coming in as text is not an issue, however, the dates changing as soon as the file is opened is problematic. I could try to import the entire .csv file as comma delimited text rather than opening the file, however, it would be easier and faster if I could stop the dates from changing when I open the file.

Flder = InputBox("Copy and Paste Folder path here:")

Set FSO = CreateObject("Scripting.FileSystemObject")
Set SourcePath = FSO.GetFolder(Flder)

For Each File In SourcePath.Files        
    Workbooks.Open (File)

    FlNm = File.Name

    StrtCol = Workbooks(FlNm).Worksheets(1).Range(Cells(4, 1), Cells(4, 30)).Find ("Mean").Column

    Workbooks(FlNm).Worksheets(1).Range(Cells(1, 1), Cells(60000, 1)).Copy (Workbooks("Find Water Years V2.xls").Worksheets(1).Range("A3"))
    Workbooks(FlNm).Worksheets(1).Range(Cells(1, StrtCol), Cells(60000, StrtCol + 1)).Copy (Workbooks("Find Water Years V2.xls").Worksheets(1).Range("B3"))

    Workbooks(FlNm).Close
Next

The problem seems to occur at the line Workbooks.Open(File).

Answer 1

Since the question has already been answered by the OP in the comments but not posted as an official answer I'll put it here in case someone else misses it like I did.

workbook = workbooks.Open(filename, Local:= true)

By setting Local = true uses the local machines date format rather than assuming mdy so in locales such as Australia (dmy) it'll change the behavior of Open()