PRB: document.lastModified Property is Unreadable with ASP

ID: Q165862

The information in this article applies to:

Active Server Pages
Microsoft Internet Information Server versions 4.0, 5.0

SYMPTOMS

The lastModified property exposed by the Internet Explorer (IE) HTML scripting object model indicates the date and time at which the sender believes the resource was last modified. When this property is referenced in a page generated by the Active Server Page framework, an unreadable value is displayed by the client browser.

CAUSE

The Active Server Page framework does not include the Last-Modified response header in its response to the client.

RESOLUTION

According to RFC 1945, Hypertext Transfer Protocol 1.0 -- HTTP/1.0, Last-Modified is an entity header field, and entity header fields are optional. Internet Explorer 3.0 does not handle the absence of this header gracefully.

Active Server Pages provides the Response Intrinsic object. Use the Response.AddHeader method to add the Last-Modified header to the HTTP response.

According to the RFC, the user agent, IE, expects times to be expressed in Greenwich Mean Time (GMT). While VBSCRIPT does provide many date and time manipulation functions, it does not provide a function to return GMT or a function to return the current time zone offset from which GMT could be derived. The following example uses JSCRIPT on the server to append the Last-Modified response header to those provided by IIS and the Active Server Page Framework. Replace the contents of the page above with the following code:


   <%@ LANGUAGE=JSCRIPT %>

   <%
      // JSCRIPT automatically formats the string as specified
      // in RFC 1945, HTTP/1.0
      // e.g. Last-Modified: Tue, 15 Nov 1994 12:45:26 GMT
      theCurrentTime = new Date()

      // convert the date to GMT
      theUTCLastModifiedTime = theCurrentTime.toGMTString()

      // Inject the header into the HTTP response
      Response.AddHeader("Last-modified", theUTCLastModifiedTime)
   %>

   <HTML>
   <BODY>
   <SCRIPT LANGUAGE=VBSCRIPT>
   document.write "Last Modified on " & document.lastModified
   </SCRIPT>
   </BODY>
   </HTML>

Save the ASP file on the server, and refresh the page in the client browser. The last modified date should now be displayed correctly.

STATUS

Microsoft has confirmed this to be a problem in Internet Explorer versions 3.0 and 3.01.

MORE INFORMATION

Steps to Reproduce Behavior

Create a file containing the following HTML code. Save it as baddate.asp into a directory that corresponds to a Virtual Root in IIS. Make sure that the Virtual Root has been granted Execute permissions in IIS:
```
   <HTML>
   <BODY>
   <SCRIPT LANGUAGE=VBSCRIPT>
   document.write "Last Modified on " & document.lastModified
   </SCRIPT>
   </BODY>
   </HTML>
 
```

Launch Internet Explorer, and enter the URL that points to this page in the following address box:

http://<server>/<vroot_name>/baddate.asp

Observe that the date appears to be corrupted.

REFERENCES

RFC 1945. Hypertext Transfer Protocol 1.0 -- HTTP/1.0.

On-line Active Server Pages documentation.

For the latest Knowledge Base articles and other support information on Visual InterDev and Active Server Pages, see the following page on the Microsoft Technical Support site:

http://support.microsoft.com/support/vinterdev/

Additional query words:

Keywords : kbASP kbJScript kbScript kbVBScript kbGrpASP kbCodeSnippet kbiis400 kbiis500
Version : winnt:4.0,5.0
Platform : winnt
Issue type : kbprb