Daylight Saving nightmare

[Ellis Dee]

This isn't really a VB6 issue, but I need to overcome it for an incremental backup I run (weekly) to various flash drives. Quick background:

My backup program is designed to support three different flash drives of three different sizes (because that's what I personally have): 2 GB, 32 GB and 128 GB. During the folder recursion, I include logic to NoRecurse some paths, exclude some subfolders, and pick and choose which flash drive(s) any given folder tree is sent to. I've stripped out this logic for the code posted here.

I just now noticed that all of a sudden my larger (80 GB) backup shows every single file as out of sync. Obviously I didn't change all 17,000+ files in the past few hours; I see the reason is because Daylight Saving just kicked in around four hours ago.

Here's a stripped down version of the recursion logic I'm using:

Private Type FILETIME
    dwLowDateTime As Long
    dwHighDateTime As Long
End Type
 
Private Type SYSTEMTIME
    wYear As Integer
    wMonth As Integer
    wDayOfWeek As Integer
    wDay As Integer
    wHour As Integer
    wMinute As Integer
    wSecond As Integer
    wMilliseconds As Long
End Type
 
Private Const MAX_PATH  As Long = 260
 
Private Type WIN32_FIND_DATA
    dwFileAttributes As Long
    ftCreationTime As FILETIME
    ftLastAccessTime As FILETIME
    ftLastWriteTime As FILETIME
    nFileSizeHigh As Long
    nFileSizeLow As Long
    dwReserved0 As Long
    dwReserved1 As Long
    cFileName As String * MAX_PATH
    cAlternate As String * 14
End Type
 
Private Declare Function FindClose Lib "kernel32" (ByVal hFindFile As Long) As Long
Private Declare Function FindFirstFile Lib "kernel32" Alias "FindFirstFileA" (ByVal lpFileName As String, lpFindFileData As WIN32_FIND_DATA) As Long
Private Declare Function FindNextFile Lib "kernel32" Alias "FindNextFileA" (ByVal hFindFile As Long, lpFindFileData As WIN32_FIND_DATA) As Long
Private Declare Function FileTimeToLocalFileTime Lib "kernel32" (lpFileTime As FILETIME, lpLocalFileTime As FILETIME) As Long
Private Declare Function FileTimeToSystemTime Lib "kernel32" (lpFileTime As FILETIME, lpSystemTime As SYSTEMTIME) As Long
 
' My data structure, as opposed to API call structures
Private Type FileType
    Group As Long
    Folder As String
    FileName As String
    FileDate As Date
    FileSize As Currency
    Flags As Long
End Type
 
Private Sub AddFolder(ByVal pstrFolder As String)
    Const MAXDWORD = &HFFFF
    Const INVALID_HANDLE_VALUE = -1
    Dim strPath As String
    Dim strFile As String
    Dim lngHandle As Long
    Dim intSearching As Integer
    Dim typFile As FileType
    Dim typFind As WIN32_FIND_DATA
 
    intSearching = 1
    lngHandle = FindFirstFile(pstrFolder & "\*.*", typFind)
    Do While lngHandle <> INVALID_HANDLE_VALUE And intSearching <> 0
        strFile = Left$(typFind.cFileName, InStr(typFind.cFileName, vbNullChar) - 1)
        If (typFind.dwFileAttributes And vbDirectory) = vbDirectory Then
            If Left$(strFile, 1) <> "." Then AddFolder pstrFolder & "\" & strFile
        Else
            Select Case strFile
                Case "desktop.ini"
                Case Else
                    With typFile
                        .Group = mlngGroup
                        .Folder = Mid$(pstrFolder, Len(mstrPrefix) + 1)
                        .FileName = strFile
                        .FileDate = StructureToDate(typFind.ftLastWriteTime)
                        .FileSize = CCur((typFind.nFileSizeHigh * MAXDWORD) + typFind.nFileSizeLow)
                    End With
                    AddFile typFile
            End Select
        End If
        intSearching = FindNextFile(lngHandle, typFind)
    Loop
    lngHandle = FindClose(lngHandle)
End Sub
 
Private Function StructureToDate(ptyp As FILETIME) As Date
    Dim typLocal As FILETIME
    Dim typSystem As SYSTEMTIME
 
    If FileTimeToLocalFileTime(ptyp, typLocal) = 1 Then
        If FileTimeToSystemTime(typLocal, typSystem) = 1 Then
            With typSystem
                StructureToDate = DateSerial(.wYear, .wMonth, .wDay) + TimeSerial(.wHour, .wMinute, .wSecond)
            End With
        End If
    End If
End Function
 
' This is the actual function I use, which includes references and data structures not included in this post
Private Sub AddFile(ptypFile As FileType, plngSource As Long)
    Dim lngMax As Long
    Dim i As Long
    
    With mtypDrive(plngSource)
        .Current = .Current + 1
        If .Current > .Files Then
            .Files = (.Files * 5) \ 4
            ReDim Preserve .File(1 To .Files)
        End If
        .File(.Current) = ptypFile
    End With
End Sub

This code correctly returns all file dates exactly like explorer shows them. Unfortunately, explorer seems to be randomly making up dates for my old haven't-touched-them-in-years files like my wallpapers.

Click the thumbnail for a comparison of the files on my hard drive vs the files I manually copied over to my Sansa Extreme 128 GB flash drive (bought on Amazon, link) a couple weeks ago:



Any ideas for how I can get proper, unchanging file dates? This is just for me on my personal computer, so any solution that works is a possibility.

For example, would it help to turn off system DST and just adjust the time manually? (Many of those unchanged files have crazy datetime changes on them, much more radical than a single hour off. Up to 9 days wrong!)