From http://www.w3schools.com (Copyright Refsnes Data)

ASP DateLastModified Property

The DateLastModified property is used to return the date and time when a specified file or folder was last modified.

Syntax

FileObject.DateLastModified

FolderObject.DateLastModified

Example for the File object

<%
dim fs,f
set fs=Server.CreateObject("Scripting.FileSystemObject")
set f=fs.GetFile("c:\test.txt")
Response.Write("File last modified on: ")
Response.Write(f.DateLastModified)
set f=nothing
set fs=nothing
%>

Output:

File last modified on: 1/10/2001 10:01:19 AM

Example for the Folder object

<%
dim fs,fo
set fs=Server.CreateObject("Scripting.FileSystemObject")
set fo=fs.GetFolder("c:\test")
Response.Write("Folder last modified on: ")
Response.Write(fo.DateLastModified)
set fo=nothing
set fs=nothing
%>

Output:

Folder last modified on: 9/19/2001 10:01:19 AM

Complete File Object Reference