Renaming multiple files in a folder

Option Explicit 

'calls main method 
Call MainMethod() 

'this is main method 
Sub MainMethod() 
Dim filePath 
Dim FSO 
Dim FolderObject 
Dim fileObject 
Dim orgFileName 
Dim newFileName 
Dim periodPosition 

Dim fileNamePart 
Dim fileExtensionPart 
Dim fileDatePart 


    'Define file path. 
    filePath = InputBox("Enter full path to the folder/directory where files are") 
    If (Right(filePath, 1) <> "\") Then filePath = filePath & "\" 


    'Create the instance of the FSO. 
    Set FSO = CreateObject("Scripting.FileSystemObject") 
     
    'Set the folder you want to search. 
    Set FolderObject = FSO.GetFolder(filePath) 

    'Loop through each file in the folder. 
    For Each fileObject In FolderObject.Files 
     
        'Get complete file name with path. 
        orgFileName = fileObject.Path 
         
        'find position of last instance of . 
        periodPosition = InStrRev(orgFileName, ".") 
         
        'using the posion of last . , get the file extension 
        fileExtensionPart = Mid(orgFileName, periodPosition) 
         
        'get the none constant part of file including the extension 
        fileDatePart = Mid(orgFileName, periodPosition - 19) 
         
        'get the constant part of file 
        fileNamePart = Left(orgFileName, periodPosition - 19 - 1) 
         
        'get the date part of the file 
        fileDatePart = Left(fileDatePart, 10) 
         
        'shift back date by a day 
        fileDatePart = formatDate(CDate(fileDatePart) - 1) 
         
        'Build the new file name. 
        newFileName = fileNamePart & fileDatePart & fileExtensionPart 
         

        'Use the MoveFile method to rename the file. 
        FSO.MoveFile orgFileName, newFileName 
    Next 

    'Cleanup the objects. 
    Set FolderObject = Nothing 
    Set FSO = Nothing 

End Sub 

Function formatDate(rawDate) 
Dim newDate 

    newDate = Year(rawDate) 
    newDate = newDate & "-" 
    newDate = newDate & Right("0" & Month(rawDate), 2) 
    newDate = newDate & "-" 
    newDate = newDate & Right("0" & Day(rawDate), 2) 

    formatDate = newDate 
End Function